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BLACKBERRY
Rubus spp., family Rosaceae

Blackberries grow wild throughout the United States, but commercial production is limited largely to Oregon and Washington with small acreages in California, Michigan, New York, New Jersey, Florida, Texas, and some other southeastern States. This acreage includes erect, semierect, semitrailing, and trailing blackberries, as well as boysenberries, loganberries, and youngberries. Production has decreased considerably from the 43,684 acres in 1959 (Darrow 1967), probably because of increased harvesting costs. In 1969, production from 6,850 acres in Washington and Oregon amounted to 41.7 million pounds valued at $6.9 million (USDA 1971).

Plant:

Cultivated and wild blackberries comprise a large but inexact number of species and hybrids. Bailey (1949*) stated that more than 400 species are known in North America. He listed eight species grown for ground cover or ornament and 31 species grown for the fruits. Many of the cultivated blackberries are hybrids.

Instead of grouping the plants according to species, most authorities group them according to growth habits. The prostrate or trailing blackberry, which may spread over brush or small shrubs in the wild state, is sometimes called "dewberry. " The erect untrained blackberry may reach a height of 10 feet.

The loganberry was considered to be a cross between the 'Antwerp' red raspberry and the 'Aughinbaugh' blackberry (Lewis and Cole 1909, Aspinwall 1911, and Logan 1955). Darrow at first (1918, 1937) considered it a kind of the Pacific Coast blackberry (R. ursinus Cham. and Schlecht.), but later he (1967) agreed that it was indeed the blackberry-raspberry cross.

The youngberry or Young dewberry is generally considered to be a cross between the 'Mammoth' and 'Mays' (syn.'Austin Mays').

Bailey (1949*) placed the loganberry and boysenberry under the subspecies loganobaccus Bailey of R. ursinus and stated that the youngberry is "probably a derivative of R. ursinus, perhaps of hybrid origin." Hence, boysenberry, loganberry, youngberry, and "dewberry" are grouped herein as blackberries.

Most blackberries have a biennial "cane" or stem rising from a perennial root system. The cane usually produces its growth the first year; the second year it bears fruit and dies back to the crown. A few thornless cultivars have been developed, but most cultivars bear stiff thorns (correctly prickles) to one-quarter inch along the branch and smaller ones on the stems and leaves. The leaves are usually deciduous, but on some cultivars they are persistent. The fruit clusters of the trailing blackberries are usually less numerous, more open, and ripen earlier than those on the erect blackberries.

The fruit consists of many one-seeded fleshy drupelets or carpers on the receptacle. In the blackberry, the receptacle, unlike that in the raspberry, is retained in the harvested fruit making it more firm than the raspberry.

Blackberry plants are usually set in rows (fig. 51). To facilitate harvest of the fruit, the vines are usually trained to a trellis or tied alongside uprights.

[gfx] FIGURE 51. - 'Lucretia' blackberries trained upright on individual posts.

Inflorescence:

The erect blackberry inflorescence is usually a cluster of 10 to 20 flowers, whereas the trailing blackberry is more likely to have 1 to 10 flowers in the cluster. Intercrossing has produced all variations of this cluster size in different types and cultivars. Also, there are many more flowers per square yard of erect than of trailing blackberries. Otherwise, the whitish flowers, 1 inch or more in diameter, are similar in size and shape. There are usually four white petals and 50 to 100 stamens clustered around and overshadowing about the same number of pistils (fig. 52). Nectar is secreted in a shallow nectar cup at the base of flower. Secretion begins just before the petals start to unfold and continues until petal fall (Percifal 1946).

Blackberry nectar and pollen are both quite attractive to pollinating insects, and the plants are a source of surplus honey for bees in some of the Southern and Pacific States. Pellett (1947*) stated that the honey was light-amber in color, had a good flavor, and was very thick and slow to granulate. Gates (19l7) indicated that some forms of blackberries are more readily visited by bees than others.

[gfx] FIGURE 52. - Longitudinal section of 'Olallie' blackberry flower, x 6, and individual floret, enlarged.

Pollination Requirements:

Some of the hybrids of blackberries are self-sterile, but many of the species are partially self-fertile (Darrow 1924, 1942, Darrow and Waldo 1948). Darrow (1967) stated that self-sterility is very widespread in wild blackberries, and he gave credit to bees for performing the necessary cross-pollination. Hedrick (1938*) called attention to the sterility in blackberries and noted that the pollen is frequently shrunken or otherwise malformed. Detjen (1916) also mentioned the variations in fertility of different blackberry groups and gave pollinating insects credit for transferring the pollen. Hartman (1923) considered most species self- fertile, but not all. He noted that insufficient pollination not only reduced the number of flowers that set but also resulted in imperfect fruit. Auchter and Knapp (1937*) mentioned that most cultivars are self- fruitful but some are self-unfruitful. Hooper (1912) pointed out that loganberries need insect pollination, and he recommended the keeping of hive bees for pollination in suburban gardens and fruit farms and where large areas of the same kind of fruits are grown. Shoemaker ( 1961 ) reported the commercial blackberry cv., 'Flordagrand', was selfunfruitful and that wild blackberries were suitable pollinators.

Whether the self-fertile cultivars are capable of pollinating themselves in the absence of pollinating insects has not been determined on all cultivars of blackberries. The structure of the blossom strongly indicates that insects are necessary to transfer the pollen from the appropriate anthers to all of the receptive stigmas if maximum production of highest quality berries is obtained. Hartman (1923) noted that the 'Mammoth' and 'Cory Thornless' cvs. of blackberries in Oregon were "more or less self-sterile and require cross-pollination. Insufficient cross-pollination of these not only reduces the total set but results in imperfect fruit. "

Shoemaker and Westgate (1966) stated that the 'Flordagrand' blackberry is self-sterile but can be pollinated with pollen from the native trailing type of blackberries, but the native plants must be growing "in quantity near the cultivated plants and overlapping must occur in bloom." The 'Oklawaha' cv. was developed precisely to provide a pollen source for 'Flordagrand' and to yield a marketable crop as well. The 'Oklawaha' sets no fruit with its own pollen but produces abundantly if cross-pollinated (Shoemaker and Westgate 1966).

Yields largely depend upon the degree of insect cross-pollination. Shoemaker and Davis (1966) stated that if a perfectly formed berry is to be obtained most or all of the pistils of the blossom must be effectively pollinated by some "mass" method such as the visits of honey bees. They recommended that colonies of honey bees be placed in or near the plantings just before bloom. They also recommended the planting of alternate rows of 'Flordagrand' and 'Oklawaha' to provide the supply of pollen for crossing. They concluded that in all of the trailing cultivars the yields depended on the degree of effective cross-pollination. Sherman and Westgate (1968) pointed out that differences in size of berries may be due to imperfect pollination.

The effective time period of pollen transfer within an individual flower, as well as between flowers of blackberries has not been determined. Most pollination probably takes place the first day the flower is open with the remainder occurring the second day, although flowers will stay receptive for 3 days in a greenhouse at 75 deg F. Petals will hang on for 4 days if the weather is cool, but they usually drop off the second or third day.

The USDA (1967) recommended the removal of all wild blackberry and raspberry plants in the vicinity of blackberry fields. From the standpoint of disease and harmful insect control, this is good advice but from the standpoint of cross-pollination and the production of the largest quantity of highest quality berries, it may be questionable if only one cultivar is in the field.

With recent development of mechanical harvesting, the need for firmer berries has been emphasized. Such berries are more likely to be obtained if they are adequately pollinated.

Pollinators:

There is little information on the pollinating insects of blackberries. Honey bees eagerly visit the blossoms if the weather is favorable and are credited with much of the cross-pollination that occurs. Bumble bees and various other wild bees also visit the flowers, but where the berries are grown commercially, there are not likely to be enough of these insects in the wild to provide the mass pollination desired for maximum crop production. Honey bee colonies can be moved to such fields as desired.

Pollination Recommendations and Practices:

Hooper (1913) and Shoemaker and Davis (1966) recommended the placement of colonies of honey bees in or near blackberry plantings, and the evidence is strong that commercial production would be enhanced by supplying adequate pollinating agents. Even selffertile cultivars can benefit by having bees transfer pollen to every receptive stigma of the blossom at the earliest possible moment. An adequate supply of pollinating insects should be highly remunerative both in volume and quality of berries produced.

The number of bee visitations per number of flowers that would provide this service is unknown, but considering the time a bee spends in a flower and the number of stigmas that need to be pollinated, the recommendation of one honey bee for each 100 (muskmelon) flowers (McGregor et al. 1965) might be a conservative recommendation on berries. Such a rate of bee visitation might require the placement of several strong healthy colonies of honey bees per acre in the field at flowering time.

LITERATURE CITED:

ASPINWALL, B.
1911. THE OREGON BOGANBERRY Oreg. State Hort. Soc. 26th Ann. Mtg., pp. 77-78.

DARROW, G. M
1918. CULTURE OF THE BOGAN BLACKBERRY U.S. Dept. Agr. Farmers' Bul. 998, 24 pp.

____ 1924. DEWBERRY GROWING. U.S. Dept. Agr. Farmers' Bul. 1402, 28 pp.

____ 1937. BLACKBERRY AND RASPBERRY IMPROVEMENT. U.S.. Dept. Agr. Yearbook 1937: 496-533.

____ 1942. BLACKBERRY GROWING. U.S. Dept. Agr. Earmers' Bul. 1399, 18 pp.

____ 1967. THE CULTIVATED RASPBERRY AND BLACKBERRY IN NORTH AMERICA; BREEDING AND IMPROVEMENT. Amer. Hort. Mag. 46(4): 203-218.

____ and WALDO, G. F.
1948. GROWING ERECT AND TRAILING BLACKBERRIES. U.S. Dept. Agr. Earmers' Bul. 1995, 34 pp.

DETJEN, L. R.
1916. SELF-STERILITY IN DEWBERRIES AND BLACKBERRIES. N.C. Agr. Expt. Sta. Tech. Bul. 11, 37 pp.

GATES, B. N.
1917. HONEY BEES IN REBATION TO HORTICULTURE. Mass. Hort. Soc. Trans. Pt. 1: 71-88.

HARTMAN, H.
1923. THE CANE FRUTT INDUSTRY IN OREGON. Oreg. Agr. Expt. Sta. Cir. 48, 28 pp.

HOOPER C. H.
1913. THE POLLINATION AND SETTING OF FRUIT BLOSSOMS AND THEIR INSECT VISITORS. Jour. Roy. Hort. Soc. 38: 238-248.

LEWIS, C. I., and COLE, C. A.
1909. CULTURE OF SMALL FRUITS. Oreg. Agr. Expt. Sta. Bul. 105, 29 pp.

LOGAN, M. E.
1955. THE LOGAN BERRY. 20 pp. M. E. Logan, Oakland, Calif.

MCGREGOR, S. E, LEVIN, M. D., and FOSTER, R. E.
1965. HONEY BEE VISITORS AND FRUIT SETTING OF CANTALOUPS. Jour. Econ. Ent. 58: 968,-970.

PERCIFAL, M. S.
1946. OBSERVATIONS ON THE FLOWERING AND NECTAR SECRETION OF RUBUS FRUTICOSUS (AGG.). New Phytol. 45: 111-123.

SHERMAN, W. B., and WESTGATE, P. J.
1968. BLACKBERRY PRODUCTION IN FLORIDA. Fla. Agr. Ext. Serv. Cir. 325,12 pp.

SHOEMAKER, J. S.
1961. POLLINATION REQUIREMENTS OF FLORDAGRAND BLACKBERRY. Fla. State Hort. Soc. Proc. 74: 356-358.

SHOEMAKER, J. S., and DAVIS, R. M.
1966. BLACKBERRY PRODUCTION IN FLORIDA. Fla. Agr. Ext. Serv. Cir. 294,20 pp.

_____ and WESTGATE, P. J.
1966. OKLAWAHA BLACKBERRY. Fla. Agr. Expt. Sta. Cir. S-159, Leaflet.

UNITED STATES DEPARTMENT OF AGRICULTURE.
1967. GROWING BLACKBERRIES. U.S. Dept. Agr. Farmers' Bul. 2160,10 pp.

_____ 1971. FRUITS. PART 1. NONCITRUS BY STATES 1969-70 U.S. Dept. Agr. Statist. Rptg. Serv. CRB FRNT 4-1 (5-71),22 pp.

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BLUEBERRY
Vaccinium spp., family Ericaceae

The blueberry industry in the United States is concerned primarily with three distinct types of blueberries: highbush, lowbush, and rabbiteye. In the lowbush type, the two most common species are V. angustifolium Ait. and V. myrtilloides Michx. The highbush type developed mainly from V. australe Small and V. corymbosum L. (Goheen 1953). The rabbiteye type consists of one species, V. ashei Reade. Some hybrids, relatively unimportant in the United States, have been considered as a halfhigh group. Darrow (1966) stated that there were millions of clones - covering tens of thousands of acres from New Hampshire to West Virginia - of segregates of highbush-lowbush hybrids that are called lowbush. Numerous other species of minor importance are mentioned in the excellent book on blueberries by Eck and Childers (1966).

The 1964 United States Census of Agriculture reported 43,114 acres of blueberries in 20 States, with production of 46 million quarts of berries valued at $15 million. However, Darrow and Moore (1962) stated: "Although the blueberry crop from all cultivated varieties had a value of more than $13 million in 1960, the total value of the industry in the United States is much greater, as wild blueberries are harvested in several widely separated areas." Further on they continued: "About 150,000 acres of native blueberries in Maine are given some care." Eck and Childers (1966, p. 5) stated: "At present more than 100,000 acres of the lowbush species are under cultivation in the United States. Two-thirds of this acreage is harvested annually, and one-third is burned over each year." These statements would indicate that the 1964 United States Census of Agriculture data dealt only with tilled acreages, whereas the wild or burned over acreages were in addition.

This would indicate that about 200,000 acres may be concerned to some degree with blueberry production in the United States.

The bulk of the lowbush berry crop comes from plants to which some attention is given, such as burning over the area every 2 to 3 years, treating with insecticides and herbicides, fertilizing, and providing insect pollination. In recent years, more attention has been given to the care and harvesting of the lowbush type than formerly. By contrast, the bulk of the highbush and rabbiteye blueberry crop comes from plants that receive intensive cultivation.

Plant:

Lowbush blueberries may be less than a foot tall, but highbush types may grow to 30 feet. With one exception, the plant is grown only for its fruit, the delicious blue-black berry, l/4 to 1 inch in diameter. The evergreen blueberry (V. ovatum Pursh), which grows along the Pacific coast, not only yields berries, but florists also use its branches of green leaves as ornamentals. The lowbush blueberry plant develops from an individual fertile seed but spreads as a single clone by underground growth to form a colony as much as 40 feet across. Most seeds develop as a result of crossfertilization, giving rise to thousands of different kinds in the field. The highbush and rabbiteye develop as individual isolated plants with one to several stems and an oval canopy of growth above.

Before the arrival of the white man on this continent, the Indians intermittently burned over the lowbush blueberry growth, their only effort at cultivation of this plant. Burning prevents overgrowth of other plants and promotes new growth by the lowbush blueberry. Unfortunately, it also destroys many pollinating insects.

Starting in 1906, highbush blueberry selections were taken from the wild and crossed and back-crossed to form improved cultivars and an intensively cultivated crop (Coville 1937). The rabbiteye blueberry, which is a southern type, has also recently been included in the intensively cultivated crops.

The fruit of a few wild highbush species, for example, V. alto- montanum Ashe and V. membranaceum Dougl., are handpicked. The berries from the lowbush plants are harvested with hand rakes. Berries from the cultivated highbush and rabbiteye types are handpicked or mechanically harvested.

Inflorescence:

The blueberry inflorescence is usually a raceme on the last several inches of a branch (fig. 53). In the mountain blueberry (V. membranaceum Dougl.), the flowers are borne singly or in palrs on the feat axis.

The white or pink petals of the flower are united to form a tubular or bell-shaped corolla, 1/4 to 1/2 inch long, that hangs open end downward before pollination (fig. 54). After the flower is pollinated, it points skyward (Oldershaw 1970). Eight to ten stamens are inserted at the base of the corolla, around a much longer style that is receptive only on its tip. Pollen is released through pores on the end of the anther, during the period of stigma receptivity. Nectar is produced in the base of the corolla; after fertilization, the ovary matures into the many-seeded blueblack berry that ripens 2 to 3 months after flowering. The berry may contain as many as 65 extremely small seed, which do not interfere with the fruit's palatability. In fact, Barker and Collins (1965) stimulated seedless fruit development with gibberellic acid, but the product was a bland fruit with only half of the expected amotlnt of sugars present. Berry size increases with seed number (Eaton 1967, Brewer and Dobson 1969a, b).

Beekeepers sometimes obtain honey crops from blueberries (Firmer and Marucci 1964). Both nectar and pollen from blueberries are attractive to bees although some cultivars are more attractive than others (Brewer 1970, Wood et al. 1967). The reason for this difference has not been determined but should be given more serious study. Incorporation of the attractive factor in new cultivars could increase berry production.

[gfx] FIGURE 53. - Branch of highbush blueberry in flower.
FIGURE 54. - Longitudinal section of 'Tifblue' rabbiteye blueberry, x 12. A, Individual anther, x 17; B, cross-section of ovary, x 12.

Pollination Requirements:

Properly pruned and nurtured highbush or lowbush blueberry plants growing under favorable conditions are capable of setting almost 100 percent of their blossoms. A set of 80 percent is required to yield an excellent commercial crop of highbush blueberries - 50 percent for lowbush - but Karmo (1957) stated that many growers do not get over 10 to 20 percent set.

Aalders and Hall (1961) and Wood (1968) found considerable self- sterility and some cross-sterility in lowbush blueberries. More specifically, Hall and Aalders (1961) found that over 5 percent of the lowbush plants were male-sterile and that 45 percent produced less than abundant pollen or practically none. With so much sterility and pollen scarcity, it becomes evident that free transfer of pollen between plants is essential to maximum fruit production.

Early in the study of blueberries, Coville (1910) stated that pollination was effected by some insect. Later, Coville (1921) observed that when blueberry flowers were pollinated with their own pollen, and fruit was obtained, the berries were smaller and later in maturing than when pollen came from another plant, and some plants were almost completely sterile to their own pollen. Bailey (1937), Beckwith (1931), Lee (1958), Phipps (1930), Phipps et al. (1932), Shaw and Bailey (1937), Schaub and Bauer (1942), and Shaw et al. (1939) also concluded that cross-pollination was a requirement for good blueberry production. This was further confirmed by Meader and Darrow (1944,1947) and Wood (1965). Eck and Childers (1966) stated that the rabbiteye blueberry is so nearly self-sterile that compatible cultivars must be interplanted. Morrow (1943) showed that even when eelfing occurred the cross- pollinated flowers produced more seeds and were larger and earlier in maturing than those produced from selfed flowers. Boller (1956) and Darrow and Moore (1962) recommended that at least two cultivars be included in every planting to provide adequate cross-pollination possibilities.

Insect pollination is essential for maximum blueberry production. Failure to produce good crops is frequently the result of poor pollination (Firmer and Marucci 1963). Chandler (1943) stated that growers frequently blame frost for their low yields when in reality poor insect pollination is the cause. The plants set more fruit, larger fruit, and set it earlier when there is adequate cross-pollination.

The blossom is well adapted for insect pollination, with its fragrance, its nectaries at the base of the corolla, and its receptive stigma and heavy pollen, both so placed in the narrow throat of the corolla that the bee must come in contact with each when foraging. The structure and position of the blossom--hanging downward with the 10 stamens forming a tight circle around the pistil, which extends beyond them-- ideally facilitates cross-pollination. A mere touch of the blossom will dislodge some of the pollen and cause it to fall downward, but the likelihood is small that it will land on the stigma of its own or another blueberry blossom, unless it falls first upon a bee's hairy body and is then transferred to the stigma. If pollination does not occur, the pistil continues to elongate until it extends beyond the corolla, which enhances its possibility of contact with pollinating insects.

Stigma receptivity may last 5 to 8 days (Merrill 1936, Moore 1964, and Wood 1962). However, if pollination does not occur within 3 days after the flower opens, fruit set is unlikely (Chandler and Mason 1964).

Knight and Scott (1964) made cross-pollination studies in the greenhouse with four cultivars under cool and warm conditions. They reported that warm temperature hastened pollen tube growth and improved fruit set. They also found that cross-pollinated fruit ripened earlier than selfed fruit. They concluded that the larger, earlier berries and increased percentage of fruit set from cross- as compared to self- pollination indicated that growers would be economically just)fied in promoting cross-pollination.

As soon as fertilization occurs, the flower begins to lose attractiveness and development of the ovary begins.

Merrill (1936) and Merrill and Johnston (1939) erroneously concluded that blueberries were self-fruitful, and they encouraged growers to plant single cultivars in solid blocks. This advice, which was still being given as late as 1959 (Johnston 1959), seriously curtailed maximum blueberry production in Michigan for years (Martin 1967).

The inability of blueberries to set commercial crops in the absence of pollinating insects is now well established in different areas and under different conditions. However, Darrow (1966) stated that much more information seems to be needed on pollination of both lowbush and highbush blueberries. This is still true.

One of the major problems in highbush blueberry pollination is that the bulk of the commercial plantings consist of solid clonal blocks, which afford little opportunity for cross-pollination. For most efficient pollination and highest production, such blocks should be interplanted with compatible cultivars. The selfsterile rabbiteye must be interplanted with compatible cultivars.

Pollinators:

There has been considerable lack of opinion in the past as to which pollinating agent is most effective in pollinating blueberries (White and Clark 1938). In Massachusetts, Beckman and Tannenbaum (1939) recorded more bumble bees (46 percent) than honey bees (38 percent) on blueberry blossoms. In Michigan, Merrill (1936) stated that both bumble bees and honey bees played a major part in blueberry pollination, but he considered bumble bees the primary agents. Wood (1961) stated that the importance of honey bees as a supplement to native bees had not been clearly established in Canada. Filmer and Marucci (1963) noted that bumble bees are good pollinators of blueberries in New Jersey, but their numbers fluctuate so they are not reliable. Later Marucci (1966) conceded that bumble bees and other wild bees were inadequate. Numerous references show that modern agricultural practices have greatly reduced the bumble bee population in many areas. Other native pollinators are usually insignificant. Brewer et al. (1969a) showed that neither airblasts nor vibrations gave a commercial fruit set for either 'Jersey' or 'Rubel'. The only recourse for adequate pollination in the absence of native pollinators is to move honey bee colonies to the blueberries.

Boulanger (1964) and Boulanger et al. (1967) noted that there were too few native pollinators to set an adequate crop in many fields in Maine, and they recommended the introduction of honey bees. Darrow and Moore (1966) also stated that, in general, native bees are inadequate and should be supplemented with one to five strong colonies of honey bees per acre. Dorr and Martin (1966) stated that the scarcity of bumble bees and other bees in Michigan blueberry plantations had previously been an important factor in limiting optimum production. They recommended both the placement of honey bee colonies in the field and bumble bee conservation practices. Eaton and Stewart (1969b) and Oldershaw (1970) mentioned the wellknown fact that bumble bees frequently "burglarize" the blossoms by cutting a hole in the base of the corolla and stealing the nectar without contributing to pollination. Honey bees frequently visit these holes so their pollinating efficiency is also reduced. Helms (1970) attributed these holes to honey bees which he - we believe erroneously - considered to be "parasites."

With the populations of bumble bees decreasing as a result of various agrotechnical factors, the repeated results of various researchers previously mentioned as well as others (Eaton and Stewart 1969a, Filmer 1963, Filmer and Swift 1963, Hansson 1969, Karmo 1958, 1966, 1972, and Marucci 1965) plus practical experience strongly indicate that the value of the honey bee has gradually become fairly well recognized in most areas as the primary pollinator of blueberries. Some questions not conclusively answered about the honey bee include the appropriate number, strength, placement, and various problems of management of the colonies to be used.

The number of colonies per acre recommended by various researchers varies and lacks strong supporting data. Wood (1971) reported no increase in perfect seeds per berry when up to eight colonies per acre of lowbush blueberries were used. Brewer et al. (1969b) compared berry production and seeds per berry with colonies per acre. They obtained 160 ounces of berries with 4.9 seeds per berry per plot in fields not supplied with bees; 290 oz with 23 seeds per berry per plot in the fields supplied with two colonies per acre; and 335 oz with 28 seeds per berry in plots of a field supplied with five colonies per acre. Yet, for unexplained reasons, they stated that slightly more than two strong colonies per acre will provide an adequate pollinating force.

Marucci (1966) recommended one colony per 2 acres of highly attractive cultivars, one colony per acre of 'Weymouth', and two colonies per acre of less attractive cultivars such as 'Coville' and 'Earliblue'. Lathrop (1950, 1954) recommended one strong colony per acre on small acreages. Darrow and Moore (1966) recommended one to five strong colonies per acre. Increased production of lowbush blueberries has been shown with up to 10 colonies per acre (Boulanger 1966).

Howell et al. (1970, 1972) introduced honey bees into cages with blueberries at 0, 25, 50, and 100 percent of full bloom. They concluded that 25 percent of full bloom is the latest time for bees to be added to insure maximum yield.

According to E. C. Martin (personal commun., 1973), there was a rather dramatic acceptance of the information on the value of bees to blueberries in Michigan following publication of papers by Martin (1966) and Dorr and Martin (1966). Within 3 years, growers of 9,000 acres of blueberries were using between 12,000 and 15,000 colonies of honey bees (Mich. Agr. Expt. Sta. 1970), and this activity was primarily responsible for that State being the leading producer of blueberries. He stated that two colonies per acre has become the accepted optimum for commercial growers, and some growers were convinced that higher numbers of colonies per acre were economical.

Boulanger (1966) compared blueberry production in fields where the colonies were shifted from one field to another every few days (rotated) with fields where the colonies were left in the field throughout the period of bloom (static). The fields were supplied with 3.5, 4.5, 7.9, and 10 colonies per acre. Production varied considerably between fields and years and within treatments, but the highest yield, 80 bu/acre, was obtained from the field that contained 10 static colonies per acre. Nevertheless, he concluded that colony rotation held promise as a future management practice. Karmo (1961) also showed that colony rotation increased blueberry production. However, Karmo (1972) suggested that the bees be present for 4 to 5 days during the peak of bloom then moved to later blooming fields for more efficient use of the bees.

Sharp (1970) reported increased efficiency in pollination by the bees when the colonies were rotated. The theory involved in this shifting of the colonies is that the first day or so after a colony is reoriented the bees forage only near the hive. This subject has not been sufficiently explored to determine if the extra effort is worthwhile. Filmer and Marucci (1963) considered one bee visitor per square yard of lowbush blueberries in full bloom on days of good weather as adequate. When the population goes below this level, they recommended supplementing the local supply of pollinators with honey bees. Eaton and Stewart (1969a) showed that some colonies of honey bees collected much more blueberry pollen than other similar colonies. The genetic inheritance of this character has not been studied although other studies have shown that the tendency to collect specific pollens is inherited.

The greatest benefit in blueberry pollination seems to be derived when there are aufficient pollinators to distribute the pollen freely, not only from anthers to stigma of self-fertile flowers, or between plants of a cultivar some of which may be self-sterile, but also between self- sterile cultivars (Hall and Aalders 1961). As Eck and Childers (1966) pointed out, when the bee population is high, the more attractive blossoms become pollinated and fall rapidly, forcing the bees to work sooner on the less attractive blossoms; thus, the higher the bee concentration the more efficient the bees become.

Pollination Recommendations and Practices:

The recommendations for the supplemental use of honey bees on blueberries range from less than one colony to five colonies per acre. Frequently, the lower recommended number seems to stem from the beekeeper's reluctance to overstock an area from the standpoint of honey production or colony buildup. The actual usage varies from none to three, and State averages of honey bee colony rentals for blueberry pollination are less than one colony per acre.

Evidence indicates that the grower would profit most, in terms of quantity and quality of berries produced, earliness of harvest, and greatest percentage harvest at first picking, if the highest possible bee population were maintained at flowering time. This might mean five or even 10 colonies per acre; doubtless under most conditions it should be greater than one or two.

Most growers make some attempt at having honey bees in or near their fields; however, this supply is seldom adequate. During optimum bee flight weather, there should be sufficient colonies to provide several bees per square yard of highbush plants in full bloom and at least one bee per square yard of lowbush plants.

LITERATURE CITED:

AALDERS, L. E., and HALL, I. V.
1961. POLLEN INCOMPATIBILITY AND FRUIT SET IN LOWBUSH BLUEBERRIES. Canad. Jour. Genet. and Cytol. 3: 300-307.

BAILEY, J. S.
1937. THE POLLINATION OF THE CULTIVATED BLUEBERRY. Amer. Soc. Hort. Sci. Proc. 35: 71 - 72.

BARKER, W. G., and COLLINS, W. B.
1965. PARTHENOCARPIC FRUIT SET IN THE LOWBUSH BLUEBERRY. Amer. Soc. Hort. Sci. Proc. 87: 229-233.

BECKMAN, W., and TANNENBAUM, L.
1939. INSECTS POLLINATING CULTIVATED BLUEBERRIES. Amer. Bee Jour. 79: 436-437.

BECKWITH, C. S.
1931. BLUEBERRY POLLINATION. N. J. Agr. Expt. Sta. Ann. Rpt.: 174.

BOILER, C. A.
1956. GROWING BLUEBERRIES IN OREGON. Oreg. Agr. Expt. Sta. Bul. 499, 20 pp.

BOULANGER, L. W.
1964. BLUEBERRY POLLINATION AND SOLITARY BEES. Maine Farm Res. 12(3): 5-11.

____ 1966. BLUEBERRY POLLINATION IN MAINE. In North Amer. Blueberry Workers' Conf. Proc., Apr. 6-7. Maine Agr. Expt. Sta. Misc. Rpt. 118: 34-36.

____ WOOD, G. W., OSGOOD, E. A. and DIRKS, C. O.
1967. NATIVE BEES ASSOCIATED WITH THE LOW-BUSH BLUEBERRY IN MAINE AND EASTERN CANADA. Maine Agr. Expt. Sta. Tech. Bul. 26, 22 pp.

BREWER J. W.
191O. FACTORS AFFECTING FERTILIZATION OF BLUE-BERRY BLOSSOMS In The Indispensable Poilinators, Ark. Agr. Ext. Serv. Misc. Pub. 127, pp. 163-170.

____ and DOBSON, R. C.
1969a. VARIETAL ATTRACTIVENESS OF BLUEBERRY BLOSSOMS TO HONEY BEES. Amer. Bee Jour. 109: 422-425.

____ and DOBSON, R. C.
1969b. SEED COUNT AND BERRY SIZE IN RELATION TO POLLINATOR LEVEL AND HARVEST DATE FOR THE HIGHBUSH BLUEBERRY, VACCINIUM CORYMBOSUM. Jour. Econ. Ent. 62: 1353-1356.

DOBSON, R. C., and NELSON, J. W.
1969a. MECHANICAL POLLINATION OF TWO HIGHBUSH BLUEBERRY CULTIVARS (VACCINIUM CORYMBOSUM). HortScience 4: 330-331.

DOBSON, R. C., and NELSON J. W.
1969b. EFFECTS OF INCREASED POLLINATOR LEVELS ON PRODUCTION OF THE HIGHBUSH BLUEBERRY, VACCINIUM CORYMBOSUM. Jour. Econ. Ent. 62: 815-818.

CHANDLER, F. B.
1943. LOWBUSH BLUEBERRIES. Maine Agr. Expt. Sta Bul. 423: 105-131.

____ and MASON, I. C.
1935. BLUEBERRY POLLINATION. Maine Agr. Expt. Sta Bul. 380: 215-216.

COVILLE F. V.
191O. EXPERIMENTS IN BLUEBERRY CULTURE. U.S. Dept. Agr. Burl Plant Indus. Bul. 193, 100 pp.

____ 1921. DIRECTIONS FOR BLUEBERRY CULTURE. U.S. Dept. Agr. Bul. 974, 24 pp.

____ 1937. IMPROVING THE WILD BLUEBERRY. U.S. Dept. Agr. Yearbook 1937: 559 - 574.

DARROW, G. M.
1966. BLUEBERRY RESEARCH In North Amer. Blueberry Workers' Conf. Proc., Apr. 6-7, Maine Agr. Expt. Sta. Misc. Rpt. 118: 4-8.

____ and MOORE, J. N.
1962. BLUEBERRY GROWING. U.S. Dept. Agr. Farmers' Bul. 1951, 33 pp.

____ and MOORE, J. N.
1966. BLUEBERRY GROWING. U.S. Dept. Agr. Farmers' Bul. 1951, 38 pp.

DORR J., and MARTIN, E. C.
1966. POLLINATION STUDIES ON THE HIGHBUSH BLUEBERRY. VACCINIUM CORYMBOSUM L. Mich. Agr. Expt. Sta. Quart. Bul. 48(3): 437-448.

EATON, G. W.
1967. THE RELATIONSHIP BETWEEN SEED NUMBER AND BERRY WEIGHT IN OPEN-POLLINATED HIGH-BUSH BLUEBERRIES. HortScience 2(1): 14-15.

____ and STEWART, M. G.
1969a HIGHBUSH BLUEBERRY POLLEN COLLECTION BY HONEYBEES. HortScience 4(2): 95.

____ and STEWART. M. G.
1969b. BLUEBERRY BLOSSOM DAMAGE CAUSED BY BUMBLEBEES. Canad. Ent. 101(2): 149-150.

ECK, P., and CHILDERS, N. F.
1966. BLUEBERRY CULTURE. 378 pp. Rutgers University Press, New Brunswick, N.J.

FILMER, R S.
1963. HONEYBEES HELP BLUEBERRY CROP. N.J. Agr. 45(2): 11.

____ and MARUCCI, P. E.
1963. THE IMPORTANCE OF HONEYBEES IN BLUEBERRY POLLINATION In 31st Ann. Blueberry Open House Proc., N.a. Agr. Expt. Sta.: 14-21.

____ and MARUCCI, P. E.
1964. HONEYBEES AND BLUEBERRY POLLINATION. In 32d Ann. Blueberry Open House Proc., N.J. Agr. Expt. Sta.: 25- 27.

____ and SWIFT, F. C.
1963. BLUEBERRY POLLINATION, LESSON 1. BLUEBERRY BLOSSOMS AND HONEYBEES = MORE BLUEBERRIES. N.J. Agr. Col. Ext. Leaflet 359, 4 pp.

GOHEEN, A. C.
1953. THE CULTIVATED HIGHBUSH BLUEBERRY. U.S. Dept. Agr. Yearbook 1953: 784-789.

HALL. I. V. and AALDERS, L. E.
1961. NOTE ON MALE STERILITY IN THE COMMON LOWBUSH BLUEBERRY VACCINIUM ANGUSTIFOLIUM AIT. Canad. Jour. Plant Sci. 41: 865.

HANSSON, A.
1969. SIGNIFICANCE OF BEE POLLINATION TO YIELD OF WILD BERRIES. In 22d Internatl, Apic. Cong. Proc., Munich, Aug., pp. 434-436.

HELMS, C. W.
1970. BEES AND BLUEBERRIES. Canad. Jour. Zool. 48(1): 185.

HOWELL, G. S., KILBY, M. W., and NELSON, J. W.
1972. INFLUENCE OF TIMING OF HIVE INTRODUCTION ON PRODUCTION OF HIGHBUSH BLUEBERRIES. HortScience 7: 129-131.

NELSON, J., and MICHAEL, K.
1970. INFLUENCE OF POLLINATION AND NUTRITIONAL STATUS ON THE YIELD AND QUALITY OF HIGHBUSH BLUEBERRIES. HortScience (See 2) 5(4): 326.

JOHNSTON, S.
1959. ESSENTIALS OF BLUEBERRY CULTURE. Mich Agr. Expt. Sta. Cir. Bul. 188, 27 pp.

KARMO, E. A.
1957. POLLINATION OF THE LOWBUSH BLUEBERRY. Nova Scotia Fruit Growers' Assoc. Ann. Rpt. 94: 93-97.

KARMO, E. A.
1958. HONEY BEES AS AN AID IN ORCHARD AND BLUEBERRY POLLINATION IN NOVA SCOTIA. In 10th Internatl. Cong. Ent. Proc. 4: 955-959. Montreal, Aug. 17-25, 1956.

____ 1961. INCREASING THE POLLINATING EFFICIENCY OF THE HONEY BEE THROUGH COLONY ROTATION. Nova Scotia Dept. Agr. and Market. Cir. 102, 4 pp.

____ 1966. THE USE OF HONEYBEES IN BLUEBERRY POLLINATION IN NOVA SCOTIA. Maine Agr. Expt. Sta Misc. Rpt. 118: 21-23, 30 - 33.

____ 1972. BLUEBERRY POLLINATION, 1972- PROBLEMS, POSSIBILITIES. Nova Scotia Dept. Agr. and Market., Hort. and Biol. Serv., Apiculture 109, 14 pp.

KNIGHT, R. J., JR., and SCOTT, D. H.
1964. EFFECT OF TEMPERATURES ON SELF- AND CROSS-POLLINATION AND FRUITING OF FOUR HIGHBUSH BLUEBERRY VARIETIES. Amer. Soc. Hort. Sci. Proc. 85: 302 - 306.

LATHROP, F. H.
1950. PRODUCING BLUEBERRIES IN MAINE. Maine Agr. Expt. Sta. Bul. 479: 16 - 18.

____ 1954. HONEY BEES AND BLUEBERRY POLLINATION. Gleanings Bee Cult. 82: 331.

LEE, W. R.
1958. POLLINATION STUDIES ON LOW-BUSH BLUEBERRIES. Jour. Econ. Ent. 51: 544 - 545.

MARTIN, E. C.
1966. HONEY BEE POLLINATION OF THE HIGHBUSH BLUEBERRY. Amer. Bee Jour. 106: 366-367.

_____ 1967. POLLINATION OF THE HIGHBUSH BLUEBERRY (VACCINIUM CORYMBOSUM L.) IN MICHIGAN. In 21st Internatl. Apic. Cong. Proc., College Park, Md., p. 483. (Abstract.)

MARUCCI. P. E.
1965. BLUEBERRY POLLINATION. In 33d Ann. Blueberry Open House Proc. N.J. Agr. Expt. Sta. 33: 16-19.

____ 1966. BLUEBERRY POLLINATION. Amer. Bee Jour. 106: 250-251, 264.

MEADER. E M., and DARROW, G. M.
1944. POLLINATION OF THE RABBITEYE BLUEBERRY AND RELATED SPECIES. Amer. Soc. Hort. Sci. Proc. 45: 267-274.

____ and DARROW, G. M.
1947. HIGHBUSH BLUEBERRY POLLINATION EXPERIMENTS. Amer. Soc. Hort. Sci. Proc. 49: 196 - 204.

MERRILL, T. A.
1936. POLLINATION OF THE HIGHBUSH BLUEBERRY. Mich. Agr. Expt. Sta. Tech Bul. 151, 34 pp.

____ and JOHNSTON. S.
1939. FURTHER OBSERVATIONS ON THE POLLINATION OF THE HIGHBUSH BLUEBERRY. Amer. Soc. Hort. Sci. Proc. 37: 617 - 619.

MICHIGAN AGRICULTURAL EXPERIMENTAL STATION.
1970. THE BOUNTIFUL BUSINESS OF BEES. Mich. Agr. Expt. Sta., Michigan Science in Action, NO. 10,18 pp.

MOORE, J. N.
1964. DURATION OF RECEPTIVITY TO POLLINATION OF FLOWERS OF THE HIGHBUSH BLUEBERRY AND THE CULTIVATED STRAWBERRY. Amer. Soc. Hort.. Sci. Proc. 85: 295-301.

MORROW E. B.
l913. SOME EFFECTS OF CROSS-POLLINATION VERSUS SELF- POLLINATION IN THE CULTIVATED BLUEBERRY. Amer. Soc. Hort. Sci. Proc. 42: 469-472.

OLDERSHAW, D.
1970. THE POLLINATION OF HIGH BUSH BLUEBERRIES In The Indispensable Pollinators, Ark. Agr. Ext. Serv. Misc. Pub. 127, pp.171-176.

PHIPPS, C. R.
1930. BLUEBERRY AND HUCKLEBERRY INSECTS. Maine Agr. Expt. Sta. Bul. 356, pp.107-232.

____ CHANDLER, F. B., and MASON, I. C.
1932. BLUEBERRY POLLINATION Maine Agr. Expt. Sta. Bul. 363: p.266.

SCHAUB, I. O., and BAUER, L. D.
1942. BLUEBERRIES EARLIER AND LARGER WHEN CROSS-POLLINATED. N.C. Agr. Expt. Sta. Ann. Rpt. 65: 53.

SHARP, N.
1970. THE POLLINATION OF LOW BUSH BLUEBERRIES. In The Indispensable Pollinators, Ark. Agr. Ext. Serv. Misc. Pub. 127, pp.177-180.

SHAW F. R., and BAILEY, J. S.
1937. THE HONEYBEE AS POLLINATOR OF CULTIVATED BLUEBERRIES. Amer. Bee Jour. 77: 30.

____ BAILEY. J. S., and BOURNE. A. I.
1939. THE COMPARATIVE VALUE OF HONEYBEES IN THE POLLINATION OF CULTIVATED BLUEBERRIES. Jour. Econ. Ent. 33: 872 - 876.

WHITE E., and CLARK, J. H.
1938. SOME RESULTS OF SELF-POLLINATION OF THE HIGHBUSH BLUEBERRY, AT WHITESBOG, NEW JERSEY. Amer. Soc. Hort. Sci. Proc. 36: 305-309.

WOOD, G. W.
1961. THE INFLUENCE OF HONEYBEE POLLINATION ON FRUIT SET OF THE LOWBUSH BLUEBERRY. Canad. Jour. Plant Sci. 41: 332 - 335.

____ 1962. THE PERIOD OF RECEPTIVITY IN FLOWERS OF THE LOWBUSH BLUEBERRY. Canad. Jour. Bot. 40.685-686.

____ 1965. EVIDENCE IN SUPPORT OF REDUCED FRUIT SET IN LOWBUSH BLUEBERRY BY POLLEN INCOMPATIBILITY. Canad. Jour. Plant Sci. 45: 601-602.

____ 1968. SELF-FERTILITY IN THE LOWBUSH BLUEBERRY. Canad. Jour. Plant Sci. 48: 431-433.

____ 1971. THE RELATIONSHIP BETWEEN POLLINATOR DENSITY AND SEED NUMBER IN LOWBUSH BLUEBERRY. HortScience 6: 413

CRAIG, D. L., and HALL, I. V.
1967. HIGHBUSH BLUEBERRY POLLINATION IN NOVA SCOTIA. In Blueberry Culture in Europe. Internatl. Symposium Working Group, Venlo, Netherlands, pp.163-168.

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CHINESE GOOSEBERRY ("KIWI")
Actinidia chinensis PIanch., family Actinidiaceae

The chinese gooseberry, or yangtao, is produced commercially on a few acres in California. It is produced on a larger scale in New Zealand (where it is called the Kiwi-berry) and in the orient. The name "gooseberry" is derived from the similarity in the taste of the fruit, not to a botanical relationship to Ribes spp. (Menninger 1 966).

Plant:

Chinese gooseberry is a vigorous, deciduous, dioecious shrub that may climb to 25 feet. It has 5-inch oval leaves that are densely hairy underneath. When young, they are bright red but change to brown toward maturity. The vine is usually trained upon a trellis or pergola (Bailey and Topping 1950). The plants are usually spaced about 15 feet apart, 175 per acre (Avent 1959), with one staminate or male plant to 5 to 10 pistillate or female plants. Smith (1961) stated that no female plant should be more than three or four plants away from a male plant.

The brownish oval 1 1/2 to 3-inch long fruit (fig. 76) may be peeled and eaten out of hand with sugar or honey, used in a salad, stewed, preserved, or used in sauces.

A single pistillate plant, if well pollinated, may produce 700 pounds of fruit in a season (Menninger 1966).

[gfx]
FIGURE 76. - Closeup of Chinese gooseberry or kiwi fruit, showing the fuzzy skin.

Inflorescence:

The five- to six-petal flower is white, changing to yellow with age, l 1/2 to 2 inches in diameter, attractive, and fragrant (fig. 77). The ovary is many celled, and it produces the fruit with many seeds. The pistillate flower can be easily recognized by the swollen ovary below the base of the petals. The staminate flowers have a vestigial ovary within the corolla, surrounded by numerous stamens. There are several styles in the pistillate flower, which are also surrounded by numerous stamens that produce no viable pollen (Schroeder and Fletcher 1 967).

[gfx]
FIGURE 77.- Longitudinal section of Chinese gooseberry, or kiwi, flowers, x 4. A, Male; B, female.

Pollination Requirements:

Pollen must be transferred from the flowers on staminate plants to those on pistillate ones, therefore both types of plants must be present in the orchard, and they must flower at the same time.

Pollinators:

Schroeder and Fletcher (1967) stated that wind and insects seem to be the pollinating agents. The general structure of the plant, and the need for numerous pollen grains on the stigma to fertilize the ovules and produce the numerous seeds, indicate that wind would be a poor pollinating agent. The flower seems ideally adapted to bee pollination.

Pollination Recommendations and Practices:

Some growers in California have colonies of honey bees placed in their plantings. The literature indicates that bees are essential.

LITERATURE CITED:

AVENT, K. L.
1959. BERRY FRUIT GROWING IN VICTORIA. Jour. Agr. (Melbourne) 57(10): 647-651, 677.

BAILEY, F.L., and TOPPING, E.
1950. CHINESE GOOSEBERRIESÑTHEIR CULTURE AND USES. New Zeal. Dept. Agr. Bul. 349, 23 pp.

MENNINGER, E. A.
1966. ACTINIDIA CHINENSIS: A PROMISING FRUIT AND SOME RELATED SPECIES. Amer. Hort. Mag. 45: 252-256.

SCHROEDER, C. A., and FLETCHER, W. A.
1967. THE CHINESE GOOSEBERRY (ACTINIDIA CHINENSIS) IN NEW ZEALAND. Econ. Bot. 21: 81 - 92.

SMITH, R. L.
1961. CHINESE GOOSEBERRY. West. Fruit Grower 15(10): 19-20.

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COFFEE
Coffea spp., family Rubiaceae

Worldwide about 90 percent of the coffee produced comes from C. arabica L., 9 percent from C. canephora Pierre ex. Froehner, and less than 1 percent from C. Iiberica Bull. ex. Hiern. Brazil produces about half of the world supply of coffee, about 1.5 million tons. The most important cultivar in Brazil is 'Mundo Novo' with about three-fourths of a million acres planted (Monaco and Carvalho 1969). The combined African states are second with about 0.8 million tons. Colombia produces about 0.5 million, and El Salvador, Guatemala, and Mexico about 0.1 million tons each. In the United States, coffee is produced to an extremely limited extent only in Hawaii and Puerto Rico. In the mid-1920's, coffee production in Puerto Rico exceeded 9,000 tons, but production diminished during World War II. It is now being rehabilitated. Production of 'Koona' coffee in Hawaii is declining.

In Africa (primarily Angola, Congo, Ivory Coast, Uganda, and Madagascar), the principal coffee is C. canephora, which is now in great demand for the manufacture of instant coffee.

Yield per acre varies enormously from over 2,000 pounds of clean coffee per acre in Hawaii to only 360 lb/acre in Brazil (Chandler 1958*, Haarer 1962, Purseglove 1968*, Wellman 1961). In the United States, consumption is approximately 16 pounds per head per annum. We import annually about 1.5 million tons.

Crane and Greene (1948-53) made an extensive review with pertinent abstracts of the literature on coffee.

Plant:

Coffee trees may grow to a height of 20 to 30 feet if unpruned, but in cultivation they are pruned to about 6 feet to facilitate harvesting of the berries. Much of the coffee in Brazil is grown in the full sun although it prospers in the shade of taller trees. Considerable care is required to keep the trees in proper productive condition. The plant is susceptible to frost, intense heat, drought, and diseases. It grows best at average temperatures of about 60 deg to 75 deg F, with 75 inches of rainfall but needs a 2- to 3-month dry period to initiate flowering. The trees are usually planted about 8 feet apart; they begin bearing at about 4 years, reach full bearing by 15 years, and may bear 6 to 100 years longer (Hearer 1962).

The fruit is a drupe (or stone fruit), but is often called a cherry or berry. It is individually picked at the proper stage of ripeness. About 5 pounds of fruit yield 1 pound of clean coffee. One cherry, usually bearing two seeds, develops from a blossom. The less-desired, one-seeded cherry is referred to as a "peaberry." The fruit is dried or processed in water to remove the skin, cleaned, and bagged for shipment and use. The beans are roasted, ground, and brewed with hot water to produce a stimulating beverage (Wellman 1961).

The taxonomy of Coffea is confused, but doubtless the three previously mentioned species are the most important. There are also many botanical varieties, mutants. and cultivars.

Inflorescence:

The fragrant white flowers occur in clusters of two to 20 in the leaf axils (fig. 81). Each flower is about an inch long by an inch deep, the tubular corolla is about 1/3-inch long and the calyx is usually made up of five flared petals, forming a starlike inflorescence. There are usually five long stamens on short, curving filaments and a long style with a two-part stigma. The stamens are attached to the corolla between the lobes so that the anthers are about the height although not necessarily close to the stigma. Pollen is shed immediately after the flower opens, and the stigma is immediately receptive. Nectar is secreted at the base of the tubular corolla, but accessible to honey bees and many other insects. Both nectar and pollen are attractive to many kinds of insects.

On sunny days, the flower generally opens early in the morning and pollen shedding starts soon afterwards. The pollen is produced in comparatively small quantities and is not sticky. It may be transported by wind and insects (Carvalho and Krug 1950). If the day is cloudy, the flower may remain closed but self-pollination can occur within the flower. Two days after opening, or fertilization within the closed flower, the parts begin to wither and fall, leaving the ovary (Hearer 1962). Krug (1935) and Montealegre (1946) suggested that the lingering of the withered blossoms on the tree is an indication of an absence of insect pollinators, whereas if the petals fall freely and soon, they have been pollinated and a good crop should be expected.

Purseglove (1968*) stated that approximately 40 percent of the flowers set fruit and are harvested as mature fruit, a certain number of buds never swell, but may persist until harvest; others fall in the early stages of growth, mainly in the first 10 weeks. Ferwerda (1951) stated that a tree may produce 10,000 to 50,000 flowers but 70 to 90 percent of them fall. This fall may be due to self-incompatibility in the flower, incompatible pollen in general, absence of pollination, or defective embryo sac. Mayne (1934) kept close observation on about 20,000 original coffee buds over a 3-year period and reported that 37.6, 41.4, and 38.6 percent of them were harvested as mature coffee.

[gfx]
FIGURE 81. - Coffee in full bloom.

Pollination Requirements:

Wellman (1961) stated that C. arabica is self-fertile, yet at times some insect pollination occurs but it is not necessary. However, he stated that the other two species, C. canephora and C. Iiberica, are self-sterile and require action of wind or insects. Ferwerda (1936) stated that C. excelsa Cheval., C. Iiberica, and C. robusta Linden [= C. canephora] were self-sterile. Haarer (1962) is in agreement with Wellman on this. Amaral (1952) showed that caged C. arabica plants produced 39 percent less coffee than open plants. Later, Amaral (1960) conducted another experiment using C. arabica, cv. 'Caturra KMC', in two flowering seasons, in which he recorded the set of fruit on branches caged to exclude bees and compared production with branches freely visited by bees. Fruit setting on the protected branches was 61.7 percent, whereas on branches visited by bees it was 75.3 percent, indicating a slightly beneficial effect. According to Free (1970*), Sein (1959) had a set of 60 percent and 70 percent on bushes caged to exclude bees and bushes not caged, respectively.

Later experiments by Amaral (1972) leave no doubt that C. arabica is definitely benefited by bee pollination. He showed that bees increased set of C. arabica cv. 'Mundo Novo' (in cages with bees) about 82 percent over trees in cages without bees.

Carvalho and Krug (1950) studied the effect of cross-pollinating agents on C. arabica and concluded that 7.3 to 9.0 percent of seed resulted from cross-pollination. They did not indicate the intensity of activity of the pollinating agents. Lower (1911) claimed that honey bees are of great value in pollinating coffee in Puerto Rico during rainy seasons. Mendes (1961) showed that tubes from foreign pollen grew faster than self pollen, thus insuring crossing.

Montealegre (1946) believed that insect pollination played a much more important role in the production of coffee in Puerto Rico than was commonly thought, and he believed that honey bees increased coffee yields; however, no data was presented to support his beliefs. Nogueira- Neto et al. (1959) concluded that the part played by insects in pollinating C. arabica cv. 'Bourbon' was of only secondary importance. Sein (1923) concluded that bees are beneficial to coffee in Puerto Rico, and Rudin (1942) reported that coffee plantations were installing colonies of honey bees for pollination of coffee in Puerto Rico. Zimmerman (1928) believed that honey bees played only a minor role in the pollination of coffee, at Least in the case of the larger plantations, and no reference is made to supplementing the number of pollinating insects in the area. The quite limited evidence indicates that C. arabica is not dependent upon pollinating insects, but under some conditions at least insects can be beneficial, possibly to a substantial degree to this species of coffee. C. canephora is self-sterile (Devreux et al. 1959, Purseglove 1968*) as is the selection reported by Krug et al. (1950) and Mendes (1949), made up of C. arabica X C. dewevrei Wildem. & Dur.

Pollinators:

Ferwerda (1948) stated that pollen transfer of the pronouncedly cross-pollinated C. robusta Linden is accomplished by wind. Carvalho and Krug (1950) concluded that insects and wind were of about equal importance in the cross-pollination of coffee in Brazil. Carvalho et al. (1969) reported 7.3 to 9.05 crossing of which 4.8 to 5.3 percent was accredited to gravity, 2 to 5 percent to wind, and 0 to 2 percent to insects. McDonald (1930) suggested that growers in East Africa keep honey bee colonies on their plantations. Lower (1911) indicated that bees benefited coffee in Puerto Rico and that colonies should be placed in the coffee plantations. Montealegre (1946) also indicated that honey bees benefited coffee in Costa Rica. Nogueira-Neto et al. (1959) stated that larger bees such as honey bees and Melipona quadrifasciata Lepeletier were more efficient pollinators of coffee in Brazil, but the overall benefit was considered rather insignificant. Sein (1923, 1959) showed that honey bees were beneficial to coffee in Puerto Rico, and Rudin (1942) stated that Costa Ricans were installing colonies of honey bees in their coffee plantations for pollination purposes. Amaral (1972) stated that honey bees were the dominant pollinating agent in the area of his studies. He further showed that colonies in the coffee groves collected predominantly coffee pollen (80 percent of the pellets identified) during the peak of flowering.

In most instances where pollination of coffee was studied, the honey bee was the most important pollinating insect visiting the flowers.

Pollination Recommendations and Practices:

The use of bees as pollinators of coffee has not been recommended on C. arabica, although the evidence indicates that a beneficial effect is obtained when pollinators were concentrated on this crop during the brief period of its flowering. Amaral recommended that honey bee colonies be placed every 100 m in the coffee grove just before flowering starts. The coffee specialist might be agreeably surprised to discover the increase derived from a large-scale community-type honey bee pollination program. The other two important species, C. canephora and C. Iiberica, are self- sterile, and they would appear to be greatly benefited by bee pollination. Considering the recent increased importance of the self-sterile African C. canephora in the production of instant coffee, the use of bees in its pollination would appear to be highly profitable.

LITERATURE CITED:

AMARAL, E.
1952. [ESSAY ON THE INFLUENCE OF APIS MELLIFERA L. ON THE POLLINATION OF THE COFFEE PLANT (PRELIMINARY NOTE).] Esc. Super. de Agr. "Lutz de Queiroz" (Sao Paulo, Brazil) Bul. 9, 6 pp. [In Portuguese.]

______ 1960. [INFLUENCE OF INSECTS ON POLLINATION OF CATURRA COFFEE.] Rev. de Agr. (Sao Paulo) 35(2): 139-147. [In Portuguese, English summary.]

______ 1972. lNSECT POLLINATION OF COFFEA ARABICA L., AND RADIUS OF ACTION OF APIS MELLIFERA LINNAEUS 1758, IN THE COLLECTION OF POLLEN IN COFFEE PLANTATIONS IN BLOOM.] 82 pp., Dept. Ent., "Lutz de Quiroz" Superior School of Agr., Sao Paulo Univ., Piracicaba S.P. Brazil. [In Portuguese, summary and general conclusions in English. ]

CARVALHO, A., and KRUG, C. A.
1950. [POLLINATING AGENTS FOR COFFEE (COFFEA ARABICA). ] Bragantia 9: 11 - 24. [In Portuguese.]

______ FERWERDA, F. P., FRAHM-LELIVELD, J. A., and others.
1969. COFFEE. In Ferwerda, F. P., and Wit, F., eds. Outlines of Perennial Crop Breeding in the Tropics, pp. 189-241. H. Veenman and Zonen, N. V., Wageningen, The Netherlands.

CRANE, J. C., and GREENE, L.
1948-53. ABSTRACTS OF SOME OF THE LITERATURE PERTAINING TO COFFEE. 2 v., 150 pp. U.S. Dept. Agr. Off. Foreign Agr. Relat. Tech. Collab. Branch.

DEVREUX, M., VALLAEYS, G., POCHET, P., and GILLES, A.
1959. RESEARCH ON THE SELF-STERILITY OF ROBUSTA COFFEE (COFFEA CANEPHORA PIERRE). Pub. lnst. Nat. Agron. Congo Belge: Ser. Sci. 78: 44. 4262 (Abstract) Plant Breed. 29(4): 837.

FERWERDA
1936. [POLLINATION IN COFFEE SPECIES GROWN IN THE DUTCH EAST INDIES.] Zuchter 8: 92 - 102. [In German.] See Crane and Green 1948 for abstract.

______ 1948. COFFEE BREEDING IN JAVA. Econ. Bot. 2(3): 258-272.

______ 1951. [FRUIT DROP IN ROBUSTA COFFEE AND ITS RELATION TO POLLENIZATION AND FERTILIZATION.] Vakblad voor Biologen 31: 123 - 130. [In Dutch.] Abstract in Euphytica 1(3): 232. 1952.

HAARER, A. E.
1962. MODERN COFFEE PRODUCTION. 495 pp. Leonard Hill, London.

KRUG, C. A.
1935. HYBRIDIZATION OF COFFEE, A PRELIMINARY STUDY OF FLOWERING HABITS AND METHODS OF CROSSING. Jour. Hered. 26: 325 - 330.

______MENDES, J. E. T., CARVALHO, A., and MENDES, A. J. T.
1950. [A NEW TYPE OF COFFEE.] Bragantia 10(1): 11-25. [In Portuguese, English summary.]

LOWER, W. V.
1911. BEEKEEPING IN PUERTO RICO. Puerto Rico Agr. Expt. Sta. Cir. 13, 31 pp.

MAYNE, W. W.
1934. ANNUAL REPORT OF THE COFFEE SCIENTIFIC OFFICER 1933-34. Mysore Coffee Expt. Sta. Bul. 12. See Crane and Green 1948 for abstract.

MCDONALD, J. H.
1930. COFFEE GROWING: WITH SPECIAL REFERENCE TO EAST AFRICA. 205 pp. East Africa Ltd., London.

MENDES A. J. T.
l919. [CYTOLOGICAL OBSERVATIONS IN COFFEE.] Bragantia 9(1-4): 25-34. [In Portuguese, English summary.]

______ 1961. [SPEED OF POLLEN TUBE PENETRATION IN COFFEE ARABICA.] Bragantia 20(1): 495 - 502. [ln Portuguese, English summary.]

MONACO, L. C., and CARVALHO A.
1969. COFFEE GENETICS AND BREEDING IN BRAZIL. Shell Pub. Health and Agr. News 12(2): 74-77.

MONTEALEGRE, M. R.
1946. [THE FERTILIZATION OF COFFEE FLOWERS.] Revista del lust. de Defensa del Cafe de Costa Rica 15: 337 - 340. [ln Spanish.]

NOGUEIRA-NETO, P., CARVALHO, A., and FILHO, H. A.
1959. [THE EFFECT OF THE EXCLUSION OF POLLINATING INSECTS ON THE YIELD OF BOURBON COFFEE.] Bragantia 18: 441 - 468. [In Portuguese, English summary.]

RUDIN, J.
1942. [BEES AS POLLINATION AGENTS IN FRUIT TREES.] Rev. Inst. Defensa Cafe de Costa Rica 12(96): 490 - 491. [ In Spanish. ]

SEIN, F., JR.
1923. [BEES IN COFFEE PLANTATIONS.] Puerto Rico Insular Sta. Cir. 79, 6 pp. [ln Spanish]

______ 1959. [DO BEES HELP COFFEE?] Hacienda 55: 36-50. [ln Spanish.]

WELLMAN, F. L.
1961. COFFEE; BOTANY CULTIVATION AND UTILIZATION. 488 pp. Leonard Hill, London.

ZIMMERMANN, A.
1928. [POLLINATION OF COFFEE TREES.] His Kaffee, ed. 2, pp. 31-34. Deutscher Auslandverlag, Hamburg. [In German.]

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CRANBERRY
Vaccinium macrocarpon Ait., family Ericaceae

The large or commercial cranberry of the United States is grown only in Massachusetts, New Jersey, Oregon, Washington, and Wisconsin. Practically all cranberries are grown commercially, as compared to many fruits and vegetables that are also produced in dooryard plantings. In 1970, 21,445 acres produced 2,038,600 barrels of cranberries, for which the growers received $23.6 million. Massachusetts led with 10,900 acres. Other producing States were Wisconsin with 5,700 acres; New Jersey, 3,100 acres; Washington, 1,000 acres; and Oregon, 745 acres.

Plant:

The cranberry plant is a low, creeping, semievergreen perennial that roots freely along the runners to form a mat. The runner sends up many slender, fruiting branches 6 to 18 inches high. Its leaves are oblong and 1/3 to 1/2 inch long. Flowers on the 1-year-old shoots (uprights or fruiting spurs) eventually produce a red globular fruit, a true berry, 1/4 to 1/2 inch in size. There may be five or six blossoms per shoot, but one to three full-sized berries per shoot (fig. 99) may result in an excellent harvest (Sibert 1967), depending upon the density of the uprights. The crop is confined to cool, moist, natural, or artificial bogs that can be flooded or drained as desired. A bog may remain productive for many successive years. Some bogs in New Jersey and on Cape Cod have been productive for more than 75 years (fig. 100).

[gfx]
FIGURE 99. - Cranberry plant with mature fruit.
FIGURRE 100. - Harvesting cranberries from a large bog.

Inflorescence:

The cranberry flower in silhouette resembles the neck and head of a crane, hence the name "craneberry," which became contracted to "cranberry" (Marucci 1967a). The tiny blossom, 1/4 to 1/3 inch in size, begins to open in the morning and is fully open in 2 hours. As it expands in opening, the petals spring spars suddenly and visibly, and within a few minutes they curl back on themselves, leaving the sexual parts of the flower, the stamens and style, exposed. The petals of newly opened flowers are white or only slightly pink. If the flower is not pollinated, these petals may hang on the vine for 2 or 3 weeks, during which time they change to a rosy pink.

The five to eight individual brownish stamens fit so closely together they form a tube (Cross 1953, Darrow et al. 1924, and Franklin 1940). As the anthers in the stamen mature, they release the dry pollen which falls out the tip of this tube. The pollen is relatively heavy and is not wind blown, nor is it likely to come in contact with its own stigma. The grain is a tetrad, or a four-part grain, apparently capable of germinating into four functional pollen tubes (Roberts and Struckmeyer 1942). For this reason, not a lot of pollen is needed to fertilize the two to three dozen ovules in the four-carpel ovary.

Marucci and Filmer (1964) and Marucci (1966) also found that flowers receiving pollen from other cultivars produced more berries per stem, and larger berries with more seed than selfed flowers. This indicated that mixed lines in the bog might be more productive than a single line. Where insect pollinators were excluded, Filmer et al. (1958) found that the berries that set had only 2.7 seeds, were small, and not uniform.

Just inside the base of the stamens is a ring of nectaries (fig. 101), surrounding the base of the style. At opening, the style is slightly shorter than the stamens. When the pollen is shed, the stigma is dry. The next day, the style lengthens so the stigma extends about 1/16 inch beyond the no- longer functioning stamens, and it becomes moist and sticky. It is not receptive to pollen until 24 to 36 hours after pollen shedding begins (Rigby and Dana, 1972).

When the bee thrusts its head and proboscis or "tongue" into the staminal tube to reach the nectar, the pollen rains down upon the bee. Then when another more advanced flower with a receptive stigma is visited, the pollen is accidentally transferred, and fertilization is accomplished. As previously stated, if the flower is not fertilized, it may hang on for 2 or 3 weeks, and the petals will take on a rosy hue. A key to identification of inadequate pollination is the presence of this pinkish cast in the field. Prompt pollination causes the petals to shed and fruit development to proceed before this can occur. The fruit ripens in a couple of months.

The production of pollen and nectar of cranberries, vital in the pollination and fruit-set of the crop, seems to vary with conditions and location. Caswell (1962) stated that the blossom secreted little nectar, in some locations practically none, but produced generous quantities of pollen. This seems to be the general rule. Bergman (1954) found that cold injury further reduced or even stopped nectar secretion. Marucci (1967a) stated that cranberry blossoms are apparently poor producers of nectar and pollen, and honey bees do not eagerly work them. Stricker (1953) stated that bees work cranberries in New Jersey only for pollen. However, Gates (1911) reported that nectar from cranberries produces a superior grade of honey. Caswell (1962) and Oertel (1967) list cranberries as a nectar and pollen source. Beekeepers occasionally obtain a reddish honey they associate with bee activity on cranberries. There seems little doubt that the plant is more attractive to honey bees for its pollen than its nectar, but if bees visited it solely for its pollen, which is available before the stigma is receptive, little pollination would occur. Shimanuki et al. (1967) showed that some colonies consistently collect more pollen from cranberries than other seemingly similar colonies. This may lead to the development of specially selected bees for cranberry pollination.

Cranberry breeders might benefit the industry by selecting plant strains that produce more nectar or that have more attractive nectar for pollinating insects.

Pollination Requirements:

Earlier publications (Eastwood 1866) made no mention of pollination of cranberries. However, Gates (1911) recommended that growers keep bees for this purpose, and Franklin (1911) concluded that bees were beneficial and he recommended the placing of colonies of honey bees near cranberry bogs at blossoming time. Later, he (1912) reported that the area from which the bees were excluded bore at least a half crop of berries, this exclusion of bees had no effect on production from the plots the following year (1914). Darrow (1924) reported that many growers in Massachusetts kept apiaries, and even though Wisconsin growers did not consider bees essential they did consider them of value in hastening pollination which resulted in more even maturity. Roberts and Struckmeyer (1942) believed that pollination was affected by wind, but this has been discounted by the various tests, which showed that plants caged to exclude bees were unproductive (Firmer and Doehlert 1955). Hutson (1924,1925,1926, 1927) devoted considerable time to cranberry pollination studies and concluded that in most instances there were sufficient wild bees in New Jersey cranberry fields, but as insurance against those years when there were insufficient wild bees, the grower should rent colonies of honey bees.

Farrar and Bain (1946, 1947) and Bain (1946) did the best work on cranberry pollination from the standpoint of showing the value of honey bees. They showed that one cage with bees produced berries at the rate of 171 barrels (bbl) per acre, whereas another cage in the same field without bees produced none. In another less productive field, the cage with bees produced 64 bbl/acre, whereas the beeless cage produced 3 bbl/acre. They recommended that the grower use one strong colony for each 2 acres of this crop.

Filmer (1949) studied the effect of four-tenths of a colony per acre on two bogs and learned that bee distribution was not uniform over the bogs. In bogs 400 feet wide, pollination decreased toward the center. He recommended that colonies be placed around, or on roadways in the middle of any bog 400 feet or more across. Later, Filmer and Doehlert (1952) showed that only 15 berries per square foot set where bees were excluded, but 90 to 152 berries set where bees were plentiful. Even at the then current rental price of $5 to $7 (with one colony per 5 acres recommended), the bees were quite profitable. One berry per square foot produces about 1 bbl/acre. Filmer and Doehlert (1959) recommended one colony for each 2 or 3 acres "if the population of wild pollinators is near normal." Filmer (1953) showed that increasing the number of colonies from one-half to one per acre increased cranberry production 12 to 34 bbl/acre.

Swenson (1958) concluded that "no bees" meant "no cranberries" and reported that by adding one colony per acre the yield was increased 50 percent, and when the population was doubled the yield increased another 60 percent.

Sibert (1967) stated that bog owners were renting about one colony per acre. Although the national average production is about 60 bbl/acre, he stated that a well-managed bog should produce 150 bbl/acre. When such high production occurred, he stated that the ground at harvest time is solid red with berries.

The data establish that bees are essential to cranberry production; in most areas there are not enough bumble bees so honey bees at the rate of one colony per acre or more should be used to supplement the native bees. Pollination must be accomplished during a 3- to 4-week period, and rain, wind, or cold almost always interferes with insect activity during this period.

Pollinators:

There is little doubt that bumble bees are excellent pollinators of cranberries; 3 per rod² are considered sufficient. Johansen and Hutt (1963) recommended the placement of bumble bee hives or other nesting domiciles around cranberry bogs, for the queens to occupy. They also recommended the planting of flowering plants nearby for bumble bees to forage on, protected from pesticides, as a means of increasing the bumble bee population. Unfortunately, bumble bee populations continue to decrease in most areas, but their activity can be supplemented with honey bees. Various other wild bees have been reported from time to time on cranberries in different locations, but none of them can be depended on as a stable source of pollinators. Because cranberries are not highly attractive to honey bees, the bee population should overflood or saturate the competing plants so the bees will visit the cranberry flowers.

Marucci (1967b) stated that flowers that do not set but remain on the plant are called "blasts," and he noted that high bee concentrations reduced the number of blasts present.

Pollination Recommendations and Practices:

The pollination recommendations for cranberries lean constantly toward the use of more colonies of honey bees per acre. Earlier recommendations called for one colony per 5 acres (Doehlert 1940), one colony per 2 to 3 acres (Firmer and Doehlert 1959), one colony per 2 acres (Cross 1953, 1966), one colony per 1 or 2 acres (Firmer 1953), and one colony per acre (Swenson 1958). Farrar and Bain (1946) stated that one strong colony per 2 acres was satisfactory, if weather conditions are favorable, but under unfavorable conditions 5 to 10 colonies per acre might be needed. Stewart (1970) and Stewart and Marucci (1970) recommended one colony per acre. In general, one strong colony per acre is currently used. Usually, by the time cranberries bloom, the honey bee colonies have become populous so that strong colonies are common.

LITERATURE CITED:

BAIN, H. F.
1946. BLOOMING AND FRUITING HABITS OF THE CRANBERRY IN WISCONSIN. Cranberries 10(9): 11, 14.

BERGMAN, H. F.
1954. FLOWERING AND FRUITING CHARACTERISTICS OF THE CRANBERRY IN NEW JERSEY. Amer. Cranberry Growers' Assoc. Proc. 84: 17-20, 22-27.

CASWELL, J. H.
1962. CASWELL BEE COMPANY - CAPE COD CRANBERRY POLLINATORS. Amer. Bee Jour. 102: 222 - 223.

CROSS C. E.
1953. CRANBERRY FLOWERS AND THE SET OF FRUIT. Cranberries 17(12): 7-9.

____ 1966. CRANBERRY FLOWERS AND POLLINATION. In Research Into Action, Mass. Univ., Col. Agr., Coop. Ext. Serv. Pub. 435, pp. 27-29.

DARROW, G. M., FRANKLIN, H. J., and MALDE, O. G.
1924. ESTABLISHING CRANBERRY FIELDS. U.S. Dept. Agr. Farmers' Bul. 1400, 37 pp.

DOEHLERT C. A.
1940. THE USE OF HONEYBEES IN CRANBERRY BOGS. Amer. Cranberry Growers' Assoc. Proc. 70th Ann. Mtg.: 32 - 36.

EASTWOOD, B.
1866. COMPLETE MANUAL FOR THE CULTIVATION OF THE CRANBERRY. 120 pp. Orange-Judd & Co., New York.

FARRAR, C. L., and BAIN, H. F.
1946. HONEYBEES AS POLLINATORS OF THE CRANBERRY Amer. Bee Jour. 86: 503-504.

FARRAR, C. L. and BAIN, H. F.
1947. HONEYBEES AS POLLINATORS OF CRANBERRIES. Cranberries 11(9): 6-7, 22-23.

FILMER, R. S.
1949. CRANBERRY POLLINATION STUDIES. Amer. Cranberry Growers' Assoc. Proc. 80th Ann. Conv.: 14 - 20.

____ 1953. CRANBERRY POLLINATION STUDIES. Amer. Cranberry Growers' Assoc. Proc. 84th Ann. Conv.: 28-36.

____ and DOEHLERT, C. A. 1952. USE OF HONEYBEES IN CRANBERRY BOGS. N.J. Agr. Expt. Sta. Bul. 764, 4 pp.

____ and DOEHLERT, C. A. 1955. USE OF HONEYBEES IN CRANBERRY BOGS. Gleanings Bee Cult. 83: 265-268.

____ and DOEHLERT, C. A. 1959. USE OF HONEYBEES IN CRANBERRY BOGS. N.J. Agr. Expt. Sta. Cir. 588, 4 pp.

FILMER, R. S., MARUCCI, P. E., and MOULTER, H.
1958. SEED COUNTS AND SIZE OF CRANBERRIES. Amer. Cranberry Growers' Assoc. Proc. 88: 22, 26-30.

FRANKLIN, H. J.
1911. STATE BOG REPORT. Cape Cod Cranberry Growers' Assoc. Ann. Rpt. 24: 16-28.

____ 1912. REPORT OF CRANBERRY SUBSTATIONS FOR 1912. Mass. Agr. Expt. Sta. Rpt. part 1: 209-234.

____ 1914. REPORTS ON EXPERIMENTAL WORK IN CONNECTIONS WITH CRANBERRIES. Mass. Agr. Expt. Sta. Bul. 150: 37-62.

____ 1940. CRANBERRY GROWING IN MASSACHUSETTS. Mass. Agr. Expt. Sta. Bul. 371: 44 pp.

GATES, B. N.
1911. THE HONEY BEE AND CRANBERRY GROWING. Cape Cod Cranberry Growers' Assoc. Ann. Rpt. 24: 28.

HUTSON, R.
1924. BEES IN FRUIT POLLINATION. Gleanings Bee Cult. 52: 290-292.

____ 1925. THE HONEYBEE AS AN AGENT IN THE POLLINATION OF PEARS, APPLES AND CRANBERRIES. Jour. Econ. Ent. 18: 387-391.

____ 1926. RELATION OF THE HONEYBEE TO FRUIT POLLINATION IN NEW JERSEY. N.J. Agr. Expt. Sta. Bul. 434, 32 pp.

____ 1927. THE USE OF HONEYBEES AS POLLINATING AGENTS ON CRANBERRY BOGS. Amer. Cranberry Growers' Assoc. Proc. 57th Ann. Conv.: 10 - 11.

JOHANSEN, C. A., and HUTT, R.
1963. ENCOURAGING THE BUMBLE BEE POLLINATOR [BOMBUS MIXTUS] OF CRANBERRIES. Wash. Agr. Ext. Serv. E.M. 2262, 2 pp.

MARUCCI, P. E.
1966. CRANBERRY POLLINATION. Cranberries 30(9): 11-13.

____ 1967a. CRANBERRY POLLINATION. Cranberries 32(7): 8 - 9.

MARUCCI, P. E.
1967b. CRANBERRY POLLINATION. Amer. Bee Jour. 107: 212-213.

____ and FILMER, R. S.
1964. PRELIMINARY CROSS POLLINATION TESTS ON CRANBERRIES. Amer. Cranberry Growers' Assoc. Proc. 91st-94th Ann. Mtg. 1961-64: 48 - 51.

OERTEL, E.
1967. NECTAR AND POLLEN PLANTS. In Beekeeping in the United States, U.S. Dept. Agr., Agr. Handb. 335, pp. 10 - 16.

RIGBY, B., and DANA, M. N.
1972. FLOWER OPENING, POLLEN SHEDDING, STIGMA RECEPTIVITY AND POLLEN TUBE GROWTH IN THE CRANBERRY. HortScience 7: 84-85.

ROBERTS, R. H., and STRUCKMEYER, B. E.
1942. GROWTH AND FRUITING OF THE CRANBERRY. Amer. Soc. Hort. Sci. Proc. 40: 373-379.

SHIMANUKI, H., LEHNERT, T., and STRICKER, M. [H.]
1967. DIFFERENTIAL COLLECTION OF CRANBERRY POLLEN BY HONEY BEES. Jour. Econ. Ent. 60: 1031-1033.

SIBERT, I.
1967. THE CRANBERRY POLLINATOR. Gleanings Bee Cult. 95: 281-282.

STEWART, J. D.
1970. CRANBERRY POLLINATION IN NEW JERSEY. In The Indispensable Pollinators. Ark. Agr. Ext. Serv. Misc. Pub. 127, pp. 181-184.

____ and MARUCCI, P. E.
1970. HONEY BEES FOR CRANBERRY POLLINATION. N.J. Agr. Expt. Sta. Cir. 588-A, 4 pp.

STRICKER, M. H.
1953. BLUEBERRY AND CRANBERRY POLLINATION. Gleanings Bee Cult. 81: 268 - 271.

SWENSON, A. A.
1958. BEES AND CRANBERRIES - A WINNING COMBINATION. Amer. Bee Jour. 98: 64.

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CURRANT
Ribes spp., family Saxifragaceae

Bailey (1949*) listed the following species of currants:

[gfx]
fix table below :

R. americanum Mill. American black currant R. aureum Pursh. golden (black) currant R. nigrum L. European black currant R. odoratum Wendl. Missouri or buffalo (black) currant R. rubrum L. northern red currant R. sativam common or garden (red or white) currant (Reichenb.) Syme

Red currants are more common in the United States, whereas black currants are produced primarily in Canada, England, and Russia. Shoemaker (1955) stated that production of currants and gooseberry in the United States amounted to about 4 million quarts from about 4,000 acres. The majority of this was currants, of which New York produced about half the total amount. The 1964 U.S. Census of Agriculture showed only about 600 commercial acres of red and golden currants, which produced 2.5 million quarts and valued at about one-half million dollars. Yields of 100 to 400 bushels per acre were obtained.

The fruit, a berry that ripens in late summer, is used primarily in jellies, jam, juice, and canning or is eaten fresh. The fruit may be from I/3 to 2/3 inch in size, oval, soft, and juicy and may contain many seeds.

This crop should not be confused with the dried currants of commerce, which is a seedless grape (Hedrick 1938*).

Plant:

The currant is a stout, woody, usually spineless deciduous shrub, 4 to 7 feet tall unless trimmed to a lower height for ease of fruit harvest. Some of the species are fragrant, but R. nigrum emits a strong unpleasant odor. The fruit (fig. 104) varies in color from black to purple and scarlet with hues and stripes of yellows, greens, and white (Bailey 1914*, v. 2, pp. 603-1200, v. 5, pp. 2423-3041). The plants are native in comparatively cold climates and are the hardiest of fruits from the standpoint of resistance to cold or changing temperatures. They do not thrive in hot or dry climates.

The growing of these crops has been prohibited in some areas because the plant serves as a host for white pine blister rust (Slate 1 933).

Cultivated red currants are set about 5 feet apart in the row; black currants, 6 to 7 feet apart, with the rows 8 to 10 feet apart (Strong 1944).

Inflorescence:

The small flowers of the black and red currants are saucerlike (open-campanulate) and whitish or greenish. The yellow flowers of R. odoratum are tubular, about one-half inch long, with the calyx tube about twice as long as the sepals. Nectar, produced in the base of the flower, and pollen, produced on the half dozen or less anthers (Thayer 1923), are both highly attractive to bees (Pellett 1947*). Zakharov (1958) stated that those cultivars with higher sugar concentration in the nectar were visited more frequently than those with low-sugar concentration. The flowers are in few- to many-flowered racemes, and the minute petals are smaller than the sepals. The extremely short stamens arise on the base of the petals and incline slightly toward the style. Style and stigma are roughly the same length on most species (Thayer 1923); however, at least in some cultivars the stigma extends beyond the anthers (Strong 1944). Apparently, the stigma is receptive about the time pollen becomes available. Some plants are dioecious.

Pollination Requirements:

Fraser (1927), apparently referring to Americangrown species, stated that currants are self-fertile, thus single cultivars could be planted in a block, even though two or more are usually planted together to extend the season. Apparently, he did not distinguish between the receptivity of the plant to its own pollen and the ability of the flower to fertilize itself without the aid of an outside agency. Philp (1933) and Strong (1944) recognized this difference for they stated that currants are self-fruitful but that they require insect application of the pollen to the stigmas. Smith and Bradt (1967*) also stated that some cultivars require transfer of pollen by an outside agency.

Much more research on the black currant (R. nigrum) has been conducted in Europe and Russia than elsewhere. Free (1970*) reviewed the pollination information on this crop, including his own work (Free 1968a). He (Free 1968a) showed that both yield and quality of black currants were improved by cross-pollination by insects. He was supported by Hughes (1966), Glushkov (1958), Williams and Child (1963), and Zakharov (1960a, b). The fruit drop of black currants 7 to 10 days after flowering was associated by Zakharov (1958) with lack of adequate insect pollination. Wellington et al. (1921), according to Free (1970*), associated fruit drop with lack of pollination. Teaotia and Luckwill (1956) concluded that seeds per berry was the main cause for variation in size of fruit and the percentage of drop of the fruit.

Pollinators:

Frequently, when currants bloom, there are few native insects to visit the flowers in numbers sufficient to adequately account for the pollination required in the production of a commercial crop. In general, the honey bee is the only insect present in numbers aufficient to be of economic importance, although at times and in certain locations bumble bees are also of value (Free 1968b). Although, as Free (1970*) indicated, a certain amount of pollen may be transferred from anthers to stigma by swaying of the plant in the wind, in general, insects, specifically bees, are necessary on most cultivars of currants. Free (1968a) showed that selfincompatibility was not a factor in black currants, but transfer is necessary of pollen to the stigma within the flowers of most cultivars. Glushkov (1958) showed that the 'Laxton' black currant set only 2.2 percent of seed (0.08 kg fruit per bush) when isolated from bees but when pollinated by bees it set 46.0 percent of the seed (1.9 kg fruit per bush).

Hughes (1966) showed a significant increase in black currant production from the presence of bees, and Zakharov (1960a) concluded that the heavy fruit drop 7 to 10 days after the end of blooming is because of a lack of adequate pollination by honey bees. Pollination by bees was always more effective than hand pollination (Zakharov 1960b). Schanderl (1956) obtained 10.9 to 17.3 times as much fruit from open bee-visited plants of R. nigrum as from those covered with a gauze screen cage, even though this species is considered self-fertile.

Although information is far from complete on the pollination of currants, it indicates that some cultivars require insect transfer of pollen within the cultivar. Most cultivars are materially benefitted by an adequate supply of pollinating honey bees or related bees, which can cause fruit to set and to be larger.

Pollination Recommendations and Practices:

Only Skrebtsova (1959) has studied the relation of insect populations to set of currants. He found that with 0.5 to 0.7 colonies per hectare, only 53 to 59 percent of the fruit set; with three colonies per hectare, the set of black currants was 88.3 percent. An increase to nine colonies per hectare, increased bee visitation but not seed set, primarily because the plants could not support additional fruit due to lack of fertility.

The demand for supplemental pollination of our crop of currants would not be great under any conceivable need; however, the evidence indicates that if maximum production is desired, maximum insect pollination should be provided. If local pollinators are insufficient, they should be supplemented with colonies of honey bees placed in or adjacent to the plantings.

LITERATURE CITED:

FRASER, S.
1927. AMERICAN FRUITS. 892 pp. Orange-Judd Publishing Co., New York.

FREE, J. B.
1968a. THE POLLINATION OF BLACK CURRANTS. Jour. Hort. Sci. 43: 69-73.

____ 1968b. THE FORAGING BEHAVIOR OF HONEYBEES (APIS MELLIFERA) AND BUMBLEBEES (BOMBUS spp.) ON BLACKCURRANTS (RIBES NIGRUM), RASPBERRIES (RUBUS IDAEUS) AND STRAWBERRIES (FRAGARIA X ANANASSA) FLOWERS. Jour. Appl. Ecol. 5: 157 - 168.

GLUSHKOV, N. M.
1958. PROBLEMS OF BEEKEEPING IN THE USSR IN RELATION TO POLLINATION. Bee World 39: 81-92.

HUGHES, H. M.
1966. INVESTIGATIONS ON THE POLLINATION OF BLACK CURRANT, VAR. 'BALDWIN'. Exp. Hort. 14: 13 - 17.

PHIL(I)P, G. L. (sic.)
1933. BRIEF SUMMARY OF CALIFORNIA POLLINATION STUDIES. In Iowa State Apiarist Rpt. 1932: 39-43.

SCHANDERL, H.
1956. [EXPERIMENTS ON THE EFFECTS OF HONEYBEES ON THE YIELD OF CULTIVATED VARIETIES OF RIBES NIGRUM.] Gartenbauwiss., Munchen, n.s. 3(3): 284-291. [In German.] AA- 96/58.

SHOEMAKER, J. S.
1955. SMALL-FRUIT CULTURE. Ed. 3, 447 pp. McGraw-Hill Book Co., Inc., New York and Toronto.

SKREBTSOVA, N. D.
1959. [BEES INCREASE THE CROP OF BLACK CURRANTS.] PchelovodstVo 36(5): 25 - 28. [In Russian.] Abstract in Biol. Abs. 35(3): 25411, p. 2234, 1960. AA-357/60.

SLATE, G. L.
1933. RED CURRANTS AND GOOSEBERRIES. N.Y. (Geneva) Agr. Expt. Sta. Cir. 112, 11 pp.

STRONG, W. J.
1914. CURRANTS AND GOOSEBERRIES. Ontario Dept. Agr. Bul. 440: 1 - 13.

TEAOTIA, S. S., and LUCKWILL, L. C.
1956. FRUIT DROP IN BLACK CURRANTS: FACTORS AFFECTING 'RUNNING OFF'. Bristol Univ., Agr. and Hort. Res. Sta. Ann. Rpt. (1955) 64: 64- 74.

THAYER, P.
1923. THE RED AND WHITE CURRANTS. Ohio Agr. Expt. Sta. Bul. 371, pp. 307 - 394.

WELLINGTON, R. [A.], HATTON, R. G., and AMOS, J. M.
1921. THE 'RUNNING OFF' OF BLACK CURRANTS. Jour. Pomol. 2: 160 - 198.

WILLIAMS. R. R., and CHILD. R. D.
1963. SOME PRELIMINARY OBSERVATIONS ON THE DEVELOPMENT OF SELF- AND CROSS-POLLINATED FLOWERS OF BLACK CURRANTS. Bristol Univ., Agr. and Hort. Res. Sta. Ann. Rpt. (1962): 59-64.

ZAKHAROV, G. A.
1958. [BEES IN THE POLLINATION OF BLACK CURRANTS AND GOOSEBERRIES.] PchelovodstVo 35(5): 29 - 33. [In Russian.] AA-179/60.

____ 1960a. [ABOUT THE VISITATION OF BLACK CURRANTS BY BEES.] PchelovodstVo 37(5): 39 - 40. [In Russian.] AA-944/63.

____ 1960b. [THE ROLE OF SUPPLEMENTAL POLLINATION WITH FOREIGN POLLEN IN INCREASING THE YIELD OF BLACK CURRANTS.] Agrobiologiya 3(123): 461-462. [In Russian. ] AA-449/63.

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GOOSEBERRY
Ribes grossularia L. and R. hirtellum Michx., family Saxifragaceae

The European gooseberry (Ribes grossularia L.) belongs almost wholly to Great Britain. The American gooseberry (R. hirtellum Michx.) is the only species of commercial significance in the United States. It is found from Newfoundland to Maryland and west to the Rockies and comprises many cultivars (Hedrick 1938*). Commercial U.S. production consists of about 200 acres, mostly in Michigan and California.

Plant:

The gooseberry is a bush-fruit grown for its large berries, which are mostly consumed green in baked pies. It is usually propagated by cuttings as the seeds are open-pollinated, and resulting plants may be quite variable. It is a cool, moisture-loving plant, adapted to cool or cold climates. Production of 300 to 600 bushels (40 Ib/bu) per acre is possible (Bailey 1915*, v. 3, pp. 1201 - 1760). Usually, production is limited to a few dooryard plants or at most a few acres. The plant has spines on the woody branches. Severe pruning is necessary to remove excess branches and growth. Little cultivation is required. About 40 cultivars have been listed (Yeager and Latzke 1933, Berger 1942).

Inflorescence:

In the spring, one to three gooseberry flowers per raceme appear during the flowering period, which lasts less than a month. The calyx tube is round, with the receptacle cup-shaped and about one-half inch across. There are four to five petals, with the same number of stamens attached to the perianth. The ovary is one-celled with numerous ovules. Both nectar and pollen are produced, and both are attractive to pollinating insects (Robbins 1931 ).

Pollination Requirements:

Yeager (1935) stated that, "So far as we know, gooseberries are all self-fertile, hence cross-pollination is unnecessary and only one variety need be grown to get a crop of fruit." He apparently was not distinguishing between self-compatibility and the ability to self-pollinate. Colby (1926) also concluded, and apparently for the same reason, that gooseberries can bear fruit without the aid of insects. Robbins (1931) stated that insects are the chief agents of pollination. Auchter and Knapp (1937*) stated, "Practically all commercial varieties of currants and gooseberries are self-fruitful and thus no provision need be made for cross-pollination." Smith and Bradt (1967*) stated that gooseberries are self-fruitful and self-pollinating. However, Zakharov (1958) showed that the percentage of ripe berries, their weight and number of seeds per berry, on the average, was greater in those varieties where bees were working during bloom.

Philp (1933) stated that gooseberries and currants are self-fruitful, but they require insect application of the pollen from the anthers to the stigma. Offord et al. (1944) stated that seed production depended on insect pollinators, and the flowers of at least four species were self- sterile. (Of 736 self-pollinated flowers not a single mature fruit was obtained, but 621 cross-pollinated flowers within the species set 286 fruits.) They concluded that all seed-bearing fruit of the four species studied, Ribes roezlii Regel, R. nevadense Kellogg, R. viscosissimum Pursh, and R. glutinosum Benth. resulted from cross-pollination by insects. "The selfed flowers were pollinated by anthers from within the same protective bag."

Although the above test was performed on different species, there are no data to infer that self-sterility of the cultivated species would be different just because the plant will produce fruit. Apparently, Yeager (1935) and Auchter and Knapp (1937*) believed that because no fruit-set problem arose on isolated cultivars, they were self-fertilizing, when in reality they might have been dependent on insects to carry pollen from plant to plant or anther to stigma within the cultivar. Apparently, insects are of value to gooseberries for maximum set.

Pollinators:

Little attention has been given to the pollinating insects on gooseberries, but considering the area in which the plants grow, honey bees should be the best pollinating agents on this plant.

Pollination Recommendations and Practices:

There are no recommendations on the use of insect pollinators on gooseberries, and it is probable that where small plantings occur there may be ample pollination. However, the data indicate that if maximum production is desired, maximum pollinator activity should be provided. If there are insufficient local pollinators, they should be supplemented with honey bees.

LITERATURE CITED:

BERGER, A. 1924. A TAXONOMIC REVIEW OF CURRANTS AND GOOSEBERRIES. N.Y. (Geneva) Agr. Expt. Sta. Bul. 109, 118 pp. COLBY, A. S. 1926. NOTES ON SELF-FERTILITY OF SOME GOOSEBERRY VARIETIES. Amer. Soc. Hort. Sci. Proc. 23d Ann. Mtg.: 138-140. OFFORD, H. R, QUICK, C. R., and Moss, V. D. 1944. SELF-INCOMPATIBILITY IN SEVERAL SPECIES OF RIBES IN THE WESTERN STATES. Jour. Agr. Res. 68: 65 - 71. PHIL(I)P, G. L. (sic.) 1933. BRIEF SUMMARY OF CALIFORNIA POLLINATION STUDIES. In lowa State Apiarist Rpt., 1932, pp. 39-43. ROBBINS, W. W. 1931. THE BOTANY OF CROP PLANTS. 639 pp. P. BlakstonÕs Son & Co., Inc., Philadelphia. YEAGER, A. F. 1935. GROWING FRUIT IN NORTH DAKOTA. N. Dak. Agr. Expt. Sta. Bul. 280, 48 pp. ______and LATZKE, E. 1933. GOOSEBERRIES: VARIETIES, BREEDING, CULTURE AND USE. N. Dak. Agr. Expt. Sta. Bul. 267, 19 pp. ZAKHAROV, G. A. 1958. BEES IN POLLINATION OF BLACK CURRANTS AND GOOSEBERRIES.] Pchelovodstvo 35: 29 - 33. [In Russian.] AA-179/60.

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GRAPES (INCLUDING RAISINS AND CURRANTS)
Vitis spp., family Vitaceae

The bulk of the grapes produced for the U.S. market are from the many cultivars of the Old World grape, or the "grape of history" (Vitis vinifera L.), grown on rootstock of American species resistant to the grape phylloxera insect (Snyder 1937). Production of table wine, and raisin grapes in California exceed by several times that of all of the other States combined. In 1969, California produced 3,600,000 tons of grapes on 457,266 acres. The leading cv. was 'Thompson Seedless' -a raisin, wine, or table grape- with 232,637 acres. Other important cvs. include other table grapes: 'Emperor' and 'Flame Tokay', and the wine grapes: 'Carignane', 'Grenoche', and 'Zinfandel'. The total production of grapes in all States was 3,902,510 tons, with a value of $273 million. The utilization of grapes was as follows: For wine and grape juice production, 2,258,757 tons; dried (raisins and currants), 1,015,200 tons; fresh, 557,179 tons; canned, 66,300 tons; and home use 5,084 tons.

Other species of grapes include the only native grape grown commercially, the muscadine grape (V. rotundifolia Michx.), the most important cv. being the 'Scuppernong', and the native bunch grape, which have been developed from one or more native species, sometimes hybridized with V. vinifera. These more important native species include V. aestivalis Michx., the summer or pigeon grape; V. labrusca L., the fox grape; V. Iincecumii Buckl., the post-oak grape; and V. vulpina L., the winter grape. Bailey (1949*) includes V. labruscana Bailey, which was derived from V. labrusca, and which is the source of the numerous cultivars grown commercially in the northeast. Hedrick (1924) stated that more than 2,000 cultivars of grapes are described in American viticultural literature and as many more in European literature.

Plant:

The grape is a climbing deciduous woody perennial, with 3- to 6- inch, heart-shaped leaves, inconspicuous panicled flowers, and a cluster of a few to 100 or more spherical or ovoid white, greenish, red, purple, or black fruit (a berry) l/4 inch to over 1 inch in size. In cultivation, the vines are frequently pruned and trained on trellises, 3 to 5 feet high, in such a way that the clusters of fruit can be harvested conveniently, some mechanically. Hundreds of cultivars are grown for different types of wine and grape juice production, other cultivars are grown for table grape use, or for drying as raisin or currant grapes.

Interplanting of cultivars is necessary for self-sterile cultivars, however, selection for increased degree of self-fertility has eliminated most of the self-sterility. Now most fields are solid plantings, sometimes scions from a single plant.

Inflorescence:

The grape flower cluster is a pyramid-like, loosely branched panicle, 1 to 10 inches long, containing up to several hundred inconspicuous greenish florets about one-quarter inch long. The floret usually has five stamens, but the number may range from two to seven (Randhawa and Sharma 1960), and five green petals (fig. 114). The stamens are about as long as the pistillate column. At the base of the ovary between the stamens are five, rarely six, yellow, fleshy nectaries. Insects are attracted to the flower by the nectar and pollen.

Kerner (1897*, p. 211) reported the unusual method of opening of the grape flower. The petals never separate at the top, but are united and serve as a domelike covering for the stamens and ovary. When these organs are mature and ready to function, the petals separate from the flower base, roll up spirally, and remain hanging together for a while like a hood which is finally thrown off by the tension in the expanding stamens. In midmorning of a warm calm day these caps fall like a gentle rain beneath the vine. Munson (1899) stated that there were three kinds of grape flowers - perfect, staminate, and pistillate.

Knuth (1908*, pp. 250-263) stated that V. vinifera flowers were complete, the stigma maturing simultaneously with the stamens but remaining receptive after the anthers have withered, making both self- and cross-pollination possible.

Pammel and King (1930*, pp. 1070 - 1072), stated that grape blossoms are visited by bees for nectar and pollen, and when the cap is released, pollen is thrown on the insect. Pellett (1947*) reported that the nectar yield, in terms of honey production to colonies of honey bees, is not great but that it is of some value. He considered the plant as a better source of pollen than nectar, with honeydew sometimes gathered from the leaves. Sharples et al. (1965) studied the pollination of the 'Cardinal' cv. of V. vinifera and concluded that bees were attracted to the flowers solely for pollen, with no functional nectaries present. Davydova (1969) also reported that honey bees visit grapes primarily for pollen.

[gfx] FIGURE 114. - Longitudinal section of the 'Robin' grape, x 20. A, Petals or hood, intact, stamens not lengthened; B, petals begining to loosen, stamens lengthened; C, petals fallen, stamens free.

Pollination Requirements:

The pollination requirements of grapes, somewhat like that of citrus (see "Citrus") are complex and for similar reasons; namely, different species, hybrids, and cultivars are involved. The pollination picture is further clouded by the fact that these have been intercrossed and selected for self-fertility, and that the observations have been reported over a long period of time, from different areas and at different stages in the development of a cultivar. Olmo (1936) spoke of one cultivar of V. vinifera that was parthenocarpic, being capable of producing fruit without pollination although its pollen was viable.

In general, V. vinifera has been considered self-fertile with the American species ranging from self-fertile to self-sterile (Beach 1892a, b, 1894, 1898; Booth 1911, Hedrick 1924). The muscadine (V. rotundifolia) is the most extensively grown example of a self-sterile species (Dearing 1938; Dickey and Loucks 1938; Husmanr 1916, 1932; Husmann and Dearing 1913, Reimer 1910; Reimer and Detjen 1910). Although Dearing (1917a, b) and Fry (1968) reported finding self-fertility in at least three muscadine selections, most cultivars now grown are self-sterile (Magoon and Snyder 1943). Other self sterile or partly self- sterile native American grape include 'Brighton', 'Herbert', and 'Salem' (Kell, 1944); 'Blue Lake' (Stover l960); and 'America', 'BarryÕ, 'Edna', 'Gaertner', 'Last Rose', 'Lindlye', 'Merrimac' and 'Munson' (Magoon and Snyder 1943).

Beach (1892a, b) thought that flowers with recurved stamens could not self but upright ones might self. Dorsey (1914) found 11 self-sterile or partly steril cultivars out of 95 with upright stamens examined, whereas only two of 37 cultivars with reflexed stamens were partly fertile. The others were sterile. This showed that although upright and recurved stamens were not positive proof that flowers were fertile or sterile, they indicated a likelihood - particularly of sterility - of those cultivars with reflexed stamens, with upright stamens being no surety of self-pollination.

In the case of the 'Ohanez' ('Almeria'), cv. of V. vinifera, there is no doubt about its self-sterility. Although pollen sprays have been used (Dunne 1942, Marriott 1950), the interplanting of other cultivars is considered better (Boehm 1960). Olmo (1943) was convinced that in at least some seasons honey bees were beneficial to this cultivar.

Probably the most thorough test of the pollination requirements of a V. vinifera cultivar was conducted by Sharples et al. (1965) on the 'Cardinal' cv. (Snyder and Harmon 1951). In this test, three mature plants were enclosed during the entire period of flowering in each of five 12- mesh-per-inch plastic screen cages containing a colony of honey bees. Five similar cages were used, which excluded all insects except those small enough to enter through the screen. The effect of pollinating insects on these plants was compared with that of five similar open plots.

The test revealed a correlation between seeds and berry weight as follows:

[gfx] fix table (spacing)

No. seeds per berry Mean weight per berry, grams 0 1.6 1 4.1 2 6.0 3 7.3 4 8.2 5 9.9

The berries in the bee cages and open plots had an average of 1.79 and 1.84 seeds each, compared to 1.65 seeds per berry in the no-bee cage. The clusters averaged 12.1 and 12.3 seedless berries in the bee cages and open plots compared to 16.1 seedless berries in the no-bee cage. This difference, though significant statistically, was not significant economically, in that the primary problem of eliminating shotberries (small, usually seedless berries) was not solved. A satisfactory crop was harvested from all vines. The effect of pollen from other grape cultivars or species was not determined but was proposed for future research.

Gladwin (1937) concluded that wind was responsible and that bees played only a minor role. Sharples et al. (1961) showed that clipping 1 cm from the inflorescence apex just before blooming was, alone, highly beneficial to quality of fruit set. Golodriga (1953) felt that different cultivars of V. vinifera reacted differently to pollinating agents.

There are other indications that even V. vinifera cultivars are benefited by insect pollination. The 'Ohanez' ('Almeria') cv. is noted for its self-sterility (Boehm 1960, Dunne 1942, Hale and Jones 1956, Magoon and Snyder 1943, Marriott 1950), but other cultivars also benefit from cross- pollination (Davydova 1969), Sosunov 1953, Steshenko 1958). Gladwin (1937) stated that cross-pollination is not only essential in self-sterile cultivars but that it is also beneficial in self-fertile cultivars. These benefits were substantiated by Iyer and Randhawa (1965), Laiok (1953), Lavrov (1956), and numerous others. Golodriga (1953) stressed the importance of selecting the proper pollenizer cultivars for those cultivars that shed or produce inferior berries. There seems to be no published information on the species and cultivars of grapes that have functional nectaries. The degree to which wind, compared to insects, is responsible for pollination and fruit set, has been established for only a handful of cultivars.

In general, modern grape specialists seem to have assumed that if some fruit set in a cluster in the absence of pollinating insects the plant was self-fertilizing, or wind pollinated, and any difference between "no special pollination problem" and "maximum production of quality fruit" was ignored.

The value of pollinating insects is given no consideration by growers of 'Thompson Seedless' grapes, yet it is well known among growers that cross-pollinated berries are long but self-pollinated ones are round and likely to shed. The degree to which insect pollinators might alter this relationship seems to have been given no consideration.

Pollinators:

There is also lack of agreement on the relative value of the pollinating agents on the cultivars of grapes known to benefit from cross- pollination. Einset (1930) insisted that insects cannot be depended upon. Gladwin (1937) gave major credit to wind and little credit to bees. Knuth (1908*, p. 250) and Munson (1899) considered both wind and insects of value, although the stigma is not adapted for wind pollination and the amount of pollen produced is small. Husmann and Dearing (1913) gave credit to a "small bee-like fly and a beetle," but later Husmann (1916) gave the credit to honey bees. Dearing (1938) considered the Halictus bee excellent but honey bees of sufficient value to warrant placing colonies in larger vineyards of V. rotundifolia and V. munsoniana J. H. Simson ex Planch. Reimer and Detjen (1910) and Olmo (1943) gave major credit to honey bees and flies, Steshenko (1958) to honey bees, Barskii (1956) reported that honey bees increased the weight of grape clusters by 23 to 54 percent, and Davydova (1969) associated pollinating insect visitation with increased yield and improved quality of grapes.

Laiok (1953) compared bee visitation and grape production of six cultivars in cages with and without bees. In five of the six cultivars, production was greater by 5 to 15 percent in cages with bees. Also, production in an open field decreased as distance from an apiary increased, with 220 kg from 10 bushes at the apiary, 180 kg at 200m, and 150 kg from 10 bushes at 600 m. On the other hand, Randhawa and Negi (1965) obtained no difference in set of open and self-pollinated plants of four cultivars.

Dearing (1938) considered Halictus bees excellent pollinators. Olmo (1943) gave considerable credit to the honey bee and a syrphid fly (Scaeva pyrastri (L.)). An across-the-board rating of insect visitors to grape flowers doubtless places the honey bee first.

Honey bees visit the flowers for pollen in the forenoon, primarily 9:30 to 11:30 a.m. (Sharples et al. 1965).

Some growers have objected to the presence of bees near their grapes under the mistaken belief that bees damage grapes, even though this claim has been disproved repeatedly for years (Clay 1886). If bees are rented for grape pollination they could easily be removed before the grapes are ripe because they do at times feed on the juice of grapes after the skin is broken.

Pollination Recommendations and Practices:

The recommendations for pollination of grapes for maximum production of highest quality fruit are not too consistent. In general, breeders have assumed that grapes were either completely self- fertilizing or were cross-pollinated by wind, so that in either case insects were considered of no value. Their assumption may be based in part on the construction of the flower, which would indicate that it is physically capable of transferring its pollen from the anthers to the stigma, or breeders may consider that a plant is self-fertile because bagged blossoms or isolated plants set fruit, without determining the maximum capability to set fruit.

In the case of most American species, and to an unknown degree the European (V. vinifera) species, there is evidence that insect visitation ranges from little or no value (Einset 1930, Sharples et al. 1965) to that of great benefit (Barskii 1956, Davydova 1969, Olmo 1943, Steshenko 1958). For example, there seems to be no doubt about the need for insect cross-pollination of the American species V. rotundifolia. Dearing (1938) recommended the placement of colonies of honey bees in larger muscadine vineyards for maximum production. Husmann (1916) also recommended the placement of colonies "here and there about the center" of muscadine vineyards of 100 acres or more. Reimer and Detjen (1910) recommended a hive of bees where "a large number of vines are maintained." Armstrong et al. (1934) and Armstrong (1935) recommended the interplanting of pollen- fertile cultivars within at least 50 feet of muscadine plants.

Steshenko (1958) stated that although grapes were normally wind- pollinated, bee visitation increased production. Sosunov (1953) and Shpakova (1961) agreed and recommended the interplanting of cultivars for maximum set. Davydova (1969) also agreed that grapes are wind- pollinated, but that bee visitation, mainly for pollen, increased yield and quality, so he recommended that one colony of honey bees be "appropriately located" per hectare. Barskii (1956) also recommended the use of honey bees but believed that one colony per 2 to 5 ha might be sufficient.

There are no recommendations for the use of bees on U.S. grapes. In most instances, cultivars are not inter-planted, and large vineyards are likely to be composed of scions of a single plant with no thought given to cross-pollination. The possible value of insect pollinators is given no consideration in grower recommendations. The evidence indicates that there may be a value, to some cultivars by such insect activity (Olmo 1943). In current agrotechnology, where the grower's net profit is a relatively low percentage of the gross income, even a minor increase becomes economically significant to him. With this thought in mind, a reappraisal of the significance of insect pollination of grapes seems to be justified.

LITERATURE CITED:

ARMSTRONG, W. D.1935. NEW VARIETIES AND POLLINATION OF MUSCADINE GRAPES. Amer. Soc. Hort. Sci. Proc. 33: 450-452. ______PICKETT, T. A., and MURPHY, M. M., JR. 1934. MUSCADINE GRAPES. Ga. Agr. Expt. Sta. Bul. 185, 29 pp. BARSKII, Y. A. S. 1956. [TRAINING BEES TO POLLINATE GRAPEVINES.] Sad i Ogorod (4): 64. [In Russian.] AA-391/61. BEACH, S. A. 1892a. THE SELF-POLLINATION OF THE GRAPE. Gard. and Forest 5: 451-452. ______ 1892b. NOTES ON SELF-POLLINATION OF THE GRAPE. N.Y. (Geneva) Agr. Expt. Sta. Ann. Rpt. 11: 597-606. ______ 1894. THE FERTILIZATION OF FLOWERS IN ORCHARDS AND VINEYARDS, ESPECIALLY IN ITS RELATION TO THE PRODUCTION OF FRUIT. N.Y. (Geneva) Agr. Expt. Sta. Ann. Rpt. 13: 633-648. ______ 1898. SELF-FERTILITY OF THE GRAPE. N Y. (Geneva) Agr. Expt. Sta. Bul. 157: 397 - 441. BOEM, E. W. 1960. SHOULD YOU POLLEN-SPRAY OHANEZ GRAPES? So. Austral. Dept. Agr. Jour. 64(5): 202-203. BOOTH, N. O. 1911. A SUGGESTION IN REGARD TO THE HISTORY OF GRAPE GROWING IN AMERICA. Amer. Soc. Hort. Sci. Proc., 18th Ann. Mtg.: 105Ñ 112. CLAY, O. M. 1886. A GRAPE-GROWER DEFENDING THE BEES. Amer. Bee Jour. 22: 469. DAVYDOVA, N. S. 1969. POSSIBILITIES OF EMPLOYING BEES TO POLLINATE VINEYARDS. In 22d Internatl. Apic. Cong. Proc., Munich, pp. 176-180. DEARING, C. 1917a. THE PRODUCTION OF SELF-FERTILE MUSCADINE GRAPES. Amer. Soc. Hort. Sci. Proc., 14th Ann. Mtg.: 30-34. ______ 1917b. MUSCADINE GRAPE BREEDING. Jour. Hered. 8: 409 - 424. ______ 1938. MUSCADINE GRAPES. U.S. Dept. Agr. Farmers' bul. 1785, 36 pp. DICKEY, R. D., and LOUCKS, K W. 1938. GRAPE GROWING IN FLORIDA. Fla Agr. Expt. Sta Bul. 324, 36 pp. DORSEY M. J. l914. POLLEN DEVELOPMENT IN VITIS WITH SPECIAL REFERENCE TO STERILITY. Minn. Agr. Expt. Sta. Bul.144, 60 pp. DUNNE, T. C. 1942. POLLEN-CONTAINING SPRAYS FOR THE CROSS-POLLINATION OF OHANEZ GRAPES. West. Austral. Dept. Agr. Jour. 19 (Ser. 2) (3): 210-213. EINSET, O. 1930. OPEN POLLINATION VS. HAND POLLINATION OF POLLEN-STERILE GRAPES. N.Y. (Cornell) Agr. Expt. Sta. Tech. Bul. 162, 14 pp. FRY, B. O. 1968. COWART, A NEW SELF-FERTILE MUSCADINE. Ga. Agr. Expt. Sta. Res. Rpt. 32, 6 pp. GLADWIN F. P. 1931. POLLINATION WITH PARTICULAR REFERENCE TO THE GRAPE. Amer. Fruit Grower 57(4): 16, 35. GOLODRIGA, P. I. 1953. [ON THE SELECTION OF POLLINIZER VARIETIES OF GRAPE.] Agrobiologiya 5: 105-110. [In Russian.] HALE, C. R., and JONES L. T. 1956. THE POLLINATION OF OHANEZ GRAPES. Jour. Agr. West. Austral. 5: 565 - 567. HEDRICK, U. P. 1924. MANUAL OF AMERICAN GRAPE-GROWING. 458 pp. The Macmillan Co., New York. HUSMANN, G. C. 1916. MUSCADINE GRAPES. U.S. Dept. Agr. Farmers' Bul. 709, 28 pp. ______ 1932. GRAPE DISTRICTS AND VARIETIES IN THE UNITED STATES U.S. Dept. Agr. Farmers' Bul. 1689, 33 pp. ______and DEARING, C. 1913. THE MUSCADINE GRAPES. U.s. Dept. Agr. Burl Plant Ind. Bul. 273, 64 pp. IYER, C. P. A., and RANDHAWA, G. S. 1965. HYBRIDIZATION STUDIES IN GRAPES: INVESTIGATIONS ON THE DIRECT INFLUENCE OF POLLEN ON SOME FRUIT AND SEED CHARACTERS. Indian Jour. Hort. 22(2): 107 - 121. KELLY, C. B. 1944. THE GRAPE IN ONTARIO. Ontario Dept. Agr. Statis. Branch Bul. 438, 38 pp. LAIOK V. D. 1953. [ON POLLINATION OF GRAPES BY HONEY BEES.] Pchelovodstvo 8: 46 - 48. [In Russian.] LAVROV, V. V. 1956. [INTERSPECIFIC POLLINATION OF GRAPES AND THE TRAINING OF BEES.] In Krishchunas, I. V., and Gubin, A. F., eds., Pollination of Agricultural Plants. MoskVa, Gos. Izd-vo. Selkhoz Lit-ry, pp. 200-203. [In Russian.] MAGOON, C. A., and SNYDER, E. 1943. GRAPES FOR DIFFERENT REGIONS. U.S. Dept. Agr. Farmers' Bul. 1936, 38 pp. MARRIOTT, P. F. 1950. POLLINATION OF TABLE GRAPES. Victoria Dept. Agr. Jour. 48(9): 391 - 394. MUNSON, T. V. 1899. INVESTIGATION IN AND IMPROVEMENT OF AMERICAN GRAPES Tex. Agr. Expt. Sta Bul. 56: 217-285. OLMO, H. P. 1936. POLLINATION AND THE SETTING OF FRUIT IN THE BLACK CORINTH GRAPE. Amer. Soc. Hort. Sci. Proc. 34: 402-404. ______ 1943. POLLINATION OF THE ALMERIA (OHANEZ) GRAPE. Amer. Soc. Hort. Sci. Proc. 42: 401-406. GRAPE 229 Literature Cited ARMSTRONG, W. D. 1935. NEW VARIETIES AND POLLINATION OF MUSCADINE GRAPES. Amer. Soc. Hort. Sci. Proc. 33: 450-452. ______PICKETT, T. A., and MURPHY, M. M., JR. 1934. MUSCADINE GRAPES. Ga. Agr. Expt. Sta. Bul. 185, 29 pp. BARSKII, Y. A. S. 1956. [TRAINING BEES TO POLLINATE GRAPEVINES.] Sad i Ogorod (4): 64. [In Russian.] AA-391/61. BEACH, S. A. 1892a. THE SELF-POLLINATION OF THE GRAPE. Gard. and Forest 5: 451-452. ______ 1892b. NOTES ON SELF-POLLINATION OF THE GRAPE. N.Y. (Geneva) Agr. Expt. Sta. Ann. Rpt. 11: 597-606. ______ 1894. THE FERTILIZATION OF FLOWERS IN ORCHARDS AND VINEYARDS, ESPECIALLY IN ITS RELATION TO THE PRODUCTION OF FRUIT. N.Y. (Geneva) Agr. Expt. Sta. Ann. Rpt. 13: 633-648. ______ 1898. SELF-FERTILITY OF THE GRAPE. N Y. (Geneva) Agr. Expt. Sta. Bul. 157: 397 - 441. BOEM, E. W. 1960. SHOULD YOU POLLEN-SPRAY OHANEZ GRAPES? So. Austral. Dept. Agr. Jour. 64(5): 202-203. BOOTH, N. O. 1911. A SUGGESTION IN REGARD TO THE HISTORY OF GRAPE GROWING IN AMERICA. Amer. Soc. Hort. Sci. Proc., 18th Ann. Mtg.: 105Ñ 112. CLAY, O. M. 1886. A GRAPE-GROWER DEFENDING THE BEES. Amer. Bee Jour. 22: 469. DAVYDOVA, N. S. 1969. POSSIBILITIES OF EMPLOYING BEES TO POLLINATE VINEYARDS. In 22d Internatl. Apic. Cong. Proc., Munich, pp. 176-180. DEARING, C. 1917a. THE PRODUCTION OF SELF-FERTILE MUSCADINE GRAPES. Amer. Soc. Hort. Sci. Proc., 14th Ann. Mtg.: 30-34. ______ 1917b. MUSCADINE GRAPE BREEDING. Jour. Hered. 8: 409 - 424. ______ 1938. MUSCADINE GRAPES. U.S. Dept. Agr. Farmers' bul. 1785, 36 pp. DICKEY, R. D., and LOUCKS, K W. 1938. GRAPE GROWING IN FLORIDA. Fla Agr. Expt. Sta Bul. 324, 36 pp. DORSEY M. J. l914. POLLEN DEVELOPMENT IN VITIS WITH SPECIAL REFERENCE TO STERILITY. Minn. Agr. Expt. Sta. Bul.144, 60 pp. DUNNE, T. C. 1942. POLLEN-CONTAINING SPRAYS FOR THE CROSS-POLLINATION OF OHANEZ GRAPES. West. Austral. Dept. Agr. Jour. 19 (Ser. 2) (3): 210-213. EINSET, O. 1930. OPEN POLLINATION VS. HAND POLLINATION OF POLLEN-STERILE GRAPES. N.Y. (Cornell) Agr. Expt. Sta. Tech. Bul. 162, 14 pp. FRY, B. O. 1968. COWART, A NEW SELF-FERTILE MUSCADINE. Ga. Agr. Expt. Sta. Res. Rpt. 32, 6 pp. GLADWIN F. P. 1931. POLLINATION WITH PARTICULAR REFERENCE TO THE GRAPE. Amer. Fruit Grower 57(4): 16, 35. GOLODRIGA, P. I. 1953. [ON THE SELECTION OF POLLINIZER VARIETIES OF GRAPE.] Agrobiologiya 5: 105-110. [In Russian.] HALE, C. R., and JONES L. T. 1956. THE POLLINATION OF OHANEZ GRAPES. Jour. Agr. West. Austral. 5: 565 - 567. HEDRICK, U. P. 1924. MANUAL OF AMERICAN GRAPE-GROWING. 458 pp. The Macmillan Co., New York. HUSMANN, G. C. 1916. MUSCADINE GRAPES. U.S. Dept. Agr. Farmers' Bul. 709, 28 pp. ______ 1932. GRAPE DISTRICTS AND VARIETIES IN THE UNITED STATES U.S. Dept. Agr. Farmers' Bul. 1689, 33 pp. ______and DEARING, C. 1913. THE MUSCADINE GRAPES. U.s. Dept. Agr. Burl Plant Ind. Bul. 273, 64 pp. IYER, C. P. A., and RANDHAWA, G. S. 1965. HYBRIDIZATION STUDIES IN GRAPES: INVESTIGATIONS ON THE DIRECT INFLUENCE OF POLLEN ON SOME FRUIT AND SEED CHARACTERS. Indian Jour. Hort. 22(2): 107 - 121. KELLY, C. B. 1944. THE GRAPE IN ONTARIO. Ontario Dept. Agr. Statis. Branch Bul. 438, 38 pp. LAIOK V. D. 1953. [ON POLLINATION OF GRAPES BY HONEY BEES.] Pchelovodstvo 8: 46 - 48. [In Russian.] LAVROV, V. V. 1956. [INTERSPECIFIC POLLINATION OF GRAPES AND THE TRAINING OF BEES.] In Krishchunas, I. V., and Gubin, A. F., eds., Pollination of Agricultural Plants. MoskVa, Gos. Izd-vo. Selkhoz Lit-ry, pp. 200-203. [In Russian.] MAGOON, C. A., and SNYDER, E. 1943. GRAPES FOR DIFFERENT REGIONS. U.S. Dept. Agr. Farmers' Bul. 1936, 38 pp. MARRIOTT, P. F. 1950. POLLINATION OF TABLE GRAPES. Victoria Dept. Agr. Jour. 48(9): 391 - 394. MUNSON, T. V. 1899. INVESTIGATION IN AND IMPROVEMENT OF AMERICAN GRAPES Tex. Agr. Expt. Sta Bul. 56: 217-285. OLMO, H. P. 1936. POLLINATION AND THE SETTING OF FRUIT IN THE BLACK CORINTH GRAPE. Amer. Soc. Hort. Sci. Proc. 34: 402-404. ______ 1943. POLLINATION OF THE ALMERIA (OHANEZ) GRAPE. Amer. Soc. Hort. Sci. Proc. 42: 401-406. 230 INSECT POLLINATION OF CULTIVATED CROP PLANTS RANDHAWA, G. S., and NEGI S. S. 1965. FURTHER STUDIES ON FLOWERING AND POLLINATION IN GRAPES. Indian Jour. Hort. 22(3/4): 287 - 308. ______and SHARMA, P. L. 1960. STUDIES ON FLOWERING AND POLLINATION IN GRAPES. Hort. Adv. 4: 21-37. REIMER, F. C. 1910. SELF-STERILITY OF ROTUNDIFOLIA GRAPES. Amer. Soc. Hort. Sci. Proc. 7th Ann. Mtg.: 27-32. ______and DETJEN, L. R. 1910. SEEF-STERILITY OF THE SCUPPERNONG AND OTHER MUSCADINE GRAPES. N.C. Agr. Expt. Sta. Bul. 209, 23 pp. SHARPLES, G. C., KUYKENDALL, J. R., TRUE, L. F., and TATE, H. F. 1961. IMPROVEMENT OF MARKET QUALITY OF CARDINAL GRAPE BY INFLORESCENCE APEX REMOVAL. Amer. Soc. Hort. Sci. Proc. 77: 316 - 321. TODD, F. E, McGREGOR, S. E., and MILNE, R. I. 1965. THE IMPORTANCE OF INSECTS IN THE POLLINATION AND FERTILIZATION OF THE CARDINAL GRAPE. Amer. Soc. Hort. Sci. Proc. 36: 321-325. SHPAKOVA, V. M. 1961. [BIOCHEMICAl ANALYSIS OF GRAPE POLLEN IN CONNECTION WITH SUPPLEMENTARY POLLINATION.] Sadov. Vinograd. i. Vinodel. (6): 26-28. [In Russian. ] AA-52/65. SNYDER, E. 1937. GRAPE DEVELOPMENT AND IMPROVEMENT. U.S. Dept. Agr. Yearbook 1937: 631-655. ______and HARMON' F. N. 1951. THE CARDINAL, CALMERIA AND BLACKROSE GRAPES FOR VINIFERA REGIONS. U.S. Dept. Agr. Cir. 882, 8 pp. SOSUNOV, V. I. 1953. [ON CROSSED POLLINATION OF GRAPES.] Sad i Ogorod 5: 26 - 27. [ln Russian.] STESHENKO, F. N. 1958. [THE ROLE OF HONEY BEES 1N CROSS-POLLINATION OF GRAPE VINES.] Pchelovodstvo 35: 37 - 40. [In Russian.] AA-182/60. STOVER, L. H. 1960. BLUE LAKEÑA NEW BUNCH GRAPE FOR FLORIDA HOME GARDENS. Fla. Agr. Expt. Sta. Cir. S-120, 10 pp.

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GUAVA
Psidium guajava L., family Myrtaceae

The guava is grown commercially in India, Brazil, British Guiana, and to a limited extent in Florida, where 2,000 to 3,000 acres are cultivated and many more thousands of acres are wild. The fruit is rich in vitamin C (two to three times the amount in fresh orange juice) and also rich in vitamins A and B with some vitamin G (Webber 1942). The fruit is consumed fresh or used in the making of jams, jellies, paste or hardened jam, and juice. The greatest commercial use is for jelly (Purseglove 1968*).

Plant:

The guava is a shallow-rooted, many branched shrub or small tree 10 to 30 feet in height. The fruit is pale green to bright yellow (fig. 115), 11/2 to 41/2 inches long, with numerous seeds embedded in the pulp (fig. 116). It is well-known in most subtropical areas of the world (Campbell 1963). The fruit, 3.7 to 8.8 oz each, may have white, pink, to dark flesh, with 8.8 to 12.5 percent soluble solids and only 0.7 to 7.5 percent of the weight in seeds (Nakasone et al. 1967).

The plants are usually spaced about 20 feet apart (100 per acre). Purseglove (1968*) stated that in India a seedling tree 8 to 10 years old will yield 400 to 500 fruit, weighing 140 to 180 pounds, in a year. Grafted or layered trees of the same age yield 1,000 to 2,000 fruits weighing 400 to 700 pounds. Its culture has been described by Ruehle (1948, 1959).

[gfx] FIGURE 115. - Guava branch, with leaves and fruit.

FIGURE 116. - variations in size and shape of guava fruit.

Inflorescence:

The white flowers, about an inch in diameter, are borne singly or in two- to three-flowered cymes. The stamens are numerous. The ovary has four to five locules with a greenish-yellow style. The capitate stigma extends above the anthers, so that self-pollination without the aid of an outside agency is unlikely (Purseglove 1968*). Hamilton and Seagrave- Smith (1954) stated that the flowers are bisexual or perfect and produce an abundance of pollen.

Pollination Requirements:

Hirano and Nakasone (1969) reported that partial self- incompatibility was found in all of the species of Psidium studied. Malo and Campbell (1968) and Hamilton and Seagrave-Smith (1954) found that self-pollination is possible but that cross-pollination by insects resulted in higher yields.

Pollinators:

Bees and other insects visit the flowers. Soubihe and Gurgel (1962) considered the honey bee to be the main pollinating agent responsible for the 25.7 to 41.3 percent crossing observed between plants. They noted, however, that this degree of crossing varied from plant to plant.

Pollination Recommendations and Practices:

There are no recommendations on the use of pollinating insects on guava although the meager information available indicates that they are necessary or at least highly beneficial for maximum production.

LITERATURE CITED:

CAMPBELL, C. W.

1963. PROMISING NEW GUAVA VARIETIES. Fla. State Hort. Soc. Proc. 76: 363-365. HAMILTON R. A., and SEAGRAVE- SMITH, H. 1954. GROWING GUAVA FOR PROCESSING. Hawaii Agr. Ext. Serv. Bul. 63, 19 pp. HIRANO, R. T., and NAKASONE, H. Y. 1969. POLLEN GERMINATION AND COMPATIBILITY STUDIES IN SOME PSIDIUM SPECIES. Amer. Soc. Hort. Sci. Proc. 94: 287-289. MALO, S. E., and CAMPBELL, C. W. 1968. THE GUAVA. Fla. Agr. Ext. Sen. Fruit Crops Fact Sheet 4, 2 pp. NAKASONE, H. Y., HAMILTON, R. A., and ITO, P. 1967. EVALUATION OF INTRODUCED CULTIVARS OF GUAVA. Hawaii Farm Sci. 16 (2): 4 - 6. RUEHLE, G. D. 1948. THE COMMON GUAVAÑA NEGLECTED FRUIT WITH A PROMISING FUTURE. Econ. Bot. 2: 306 - 325. ______ 1959. GROWING GUAVAS IN FBORIDA. Fla. Agr. Ext. Serv. Bul. 17O, 32 pp. SOUBIHE, J., and GURGEI,, J. J. A. 1962. [THE EXTENT OF NATURAL CROSS-POLLINATION IN GUAVA (PSIDIUM GUAJAVA L.] Bragantia 21: 15 - 20. [In Spanish, English summary. ] WEBBER H. J. 1912. EXTENDING GUAVA PRODUCTION TO CABIFORNIA. Amer. Soc. Hort. Sci. Proc. 41: 228-233.

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HUCKLEBERRY

Gaylussacia spp., family Ericaceae

There are more than 40 species of U.S. huckleberries. In general appearance, they are so similar to blueberries that the common names are sometimes interchanged (fig. 117). The important difference between the two is in the ripe fruit. The huckleberry has 10 relatively large bony seeds that makes the fruit objectionable for some people to eat, whereas the blueberry may have as many as 65 seeds, but they are small and not objectionable (Darrow and Moore 1962, Eck and Childers 1966). Huckleberries are not usually cultivated. The fruit is harvested from wild plants in some areas and sold locally for use in pies.

From an economic standpoint, the value of huckleberries harvested and sold, although unknown, is unquestionably not great. The fruit is of considerable value to wildlife, and the flowers a source of pollen and nectar for bees.

[gfx] FIGURE 117. - Huckelberry bush, with mature fruit.

Plant:

Three species of huckleberries are of particular interest: the black or common huckleberry (G. baccata (Wang.) K. Koch), the box huckleberry (G. brachycera (Michx.) Gray), and the dwarf huckleberry (G. dumosa (Andr.) T. & G.) (Jannson 1947).

Where the black or the dwarf huckleberries occur in conjunction with the lowbush blueberry, they are considered a weed and destroyed because of the objectionable large seeds and black fruit (Phipps 1930).

From a botanical point of view, the box huckleberry is the most famous. Adams (1949) described one plant (colony) "estimated to be 13,000 years old, unquestionably the oldest thing alive on earth." (See also Mickalitis 1952.) The age is apparently more in reference to the colony than to any specific axis cross section.

The black huckleberry occurs from the Atlantic Coast west to Wisconsin and south to Louisiana. It is about 3 feet tall, much branched, with dotted leaves, slender reddish flowers, and black fruit.

The box huckleberry forms a low, dark-green carpet 2 feet high, has pinkish flowers, light-blue fruit, and spreads up to 6 inches per year by underground runners.

The dwarf huckleberry is a low plant, usually 1 to 2 feet tall, that bears long, white flower clusters. It yields large quantities of 1/4 -to l/3- inch black huckleberries that are used primarily in pies.

Inflorescence:

The 1/4 - to l/2 -inch flowers of the huckleberry are white to reddish and in axillary racemes. The tubular calyx is five-lobed, with 10 stamens surrounding a single stigma. Nectar is secreted at the base of the corolla. The flowers are attractive to bees for both their nectar and pollen.

Pollination Requirements:

The box huckleberry is self-sterile. When cross-pollinated within the clone, only nonviable seed is produced. Viable seed develop only if pollen is transferred from the anthers of one clone to the stigma of another (Adams 1949). Little is known about the pollination requirements of the black or dwarf huckleberries, but because of the similarity of the blueberry and huckleberry flowers in many other respects, future studies will probably establish that the pollination requirements are also similar.

Pollinators:

Honey bees are attracted to huckleberry flowers and are probably the primary pollinating agents under most conditions. Currently, there is no known pollination problem because the plants usually grow in the wild state, and the potential versus actual production as a result of insect pollination is unknown.

Pollination Recommendations and Practices:

None.

LITERATURE CITED:

ADAMS, J. W.

1949. THE UNIQUE BOX HUCKLEBERRY (GAYLUSSACIA BRACHYCERA). Plants and Gard. (n.s.) 5: 166-168. DARROW, G. M., and MOORE, J. N. 1962. BLUEBERRY GROWING U.S. Dept. Agr. Farmers' Bul. 1951, 33 pp. ECK, P., and CHILDERS, N. F. 1966. BLUEBERRY CULTURE. 378 pp. Rutgers University Press, New Brunswick, N.J. JANNSON, K. P. 1947. HUCKLEBERRIES, EDIBLE AND ORNAMENTAL. Plants and Gard. (N.S.) 3(1): 39-40.

MICKALITIS, A. B.1952. BOX HUCKELBERRY (G. BRACHYCERA) MOST UNIQUE SHRUB NATIVE TO PENNSYLVANIA. Forests and Waters 4: 45.

PHIPPS, C. R. 1930. BLUEBERRY AND HUCKELBERRY INSECTS. Maine Agr. Expt. Sta. Bul. 356: 107-232.

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JUJUBE, TSAO, OR CHINESE DATE
Zizphus jujuba Mill., family Rhamnaceae

The common jujube, tsao, or Chinese date, is grown occasionally in the Southern States and California for its edible fruits or as an ornamental. No great importance is attached to this fruit in the United States.

Plant:

The jujube is a small dicidous tree that may grow to 30 feet tall. It may have spines at the base of the strongly three-veined alternate leaves. The rather dry, edible, ovoid, orange to brown 1/2 to 11/2- inch long fruit is simialr to a plum or date. It has white flesh and a hard, two-celled stone. The fruit is eaten fresh, in cakes, candied, or used as a dessert. It makes a refreshing drink and is rich in vitamin C (Purseglove 1968*).

Inflorescence:

The flowers appear about mid-May at Chico, Calif., and reach their peak within 2 to 3 weeks but may continue sporadically until August. They are small greenish to yellow, in short axillary cymes, with five sepals, five petals, five stamens, and a two-celled ovary with a two-part style (fig. 118).

Ackerman (1961), who made a rather thorough study of this plant, stated that the anthers dehisce as soon as the flower opens but that the stigma becomes receptive and nectar secretion starts sometime later (Thomas 1924), with little fruit set after the first 24 hours.

[gfx] FIGURE 118. - Longitudinal section of jujube flower, x 20.

Pollination Requirements:

Ackerman (1961) noted that some clones develop fruit from self-pollinated flowers but few set appreciable crops by this means. Such fruit is usually smaller than normal and tends to drop prematurely. He concluded that cross-fertilization between compatible clones was essential for the developement of viable seed and the setting of a full crop of fruit.

Pollinators:

Ackerman (1961) stated that flies and beetles were of no value as pollinators of jujubes. He used honey bees.

Pollination Recomendations and Practices:

None.

LITERATURE CITED:

ACKERMAN, W. L. 1961. FLOWERING, POLLINATION, SELF-STERILITY AND SEED DEVELOPEMENT OF CHINESE JUJUBES. Amer. Soc. Hort. Sci. Proc. 77: 265-269.

THOMAS, C. C. 1924. THE CHINESE JUJUBE. U. S. Dept. Agr. Dept. Bul. 1215, 30 pp.

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KENAF
Hibiscus cannabinus L., family Malvaceae

Kenaf has been grown for centuries throughout the world as a fiber crop. A few thousand acres are grown in Florida for bean poles (Killinger 1969). Recently, it has been tested as a silage crop and for paper pulp (Killinger 1965,1967). In general, kenaf is grown between 45deg N and 30deg S latitudes (Purseglove 1968*).

Plant:

Kenaf is an erect herbaceous annual, 4 to 22 feet tall (Pate et al. 1954, Killinger 1965), with straight and slender green, red, or purple prickly stems. It is photoperiodic, flowering on shortening days of 12.5 hours or less. When grown for seed, 700 to 800 lb/acre have been harvested. The fruit is a capsule of several carpers, each producing several seeds.

When grown for bean poles or forage, the plant, itself, is harvested (Killinger 1967). About 200,000 poles per acre are harvested when the plant is about 10 feet tall and before it blooms. Only when seed production is desired is the plant allowed to remain through flowering and until the pods are ripe and harvested. Killinger (1969) stated that some cultivars are ready for harvest in early July to early September from seeds planted March 27 to April 5 (120 to 160 days), whereas other cultivars are ready within 60 days, and still other cultivars produce seed and are dead within 100 days after planting.

Inflorescence:

The flowers, similar to those of cotton, okra, or the common hollyhock (Althea rosea (L.) Cav.), are large (7.5 to 10 cm) with five yellow or red petals with crimson-centers. They usually open just before daybreak, begin to close about midday, and are closed by mid-afternoon never to open again. Within the corolla, the staminal column, with its short stamens, surrounds the style. The anthers release pollen about the time the flower opens, and the style emerges shortly thereafter. Then, the five-part stigma expands; the lobes become turgid but do not touch the anthers. The corolla closes spirally so that the anthers are pressed into contact with the stigma, and, if cross-pollination has not occurred, self- pollination may result. However, Ochse et al. (1961 *) stated that pollen of the same flower is seldom found on the stigma. Nectar is secreted at the base of the corolla. Nesmeyanova (1968) stated that only the nectaries on the outside of the calyx were well visited by bees, but Jones and Tamargo (1954) and Tamargo and Jones (1954) stated that honey bees visited within the blossom sufficiently to be considered efficient pollinators.

Pollination Requirements The pollination requirement of kenaf is not too well worked out. Pate and Joyner (1958) stated that kenaf has been classified on several occasions as a self-pollinated crop, but that more recently it has been classified as an often cross-pollinated crop. In a hand-pollination experiment, Dubey and Singh (1968) observed that some setting began by 11 p.m. and extended to the next 2 p.m., but only between 5 and 9 a.m. did more than 50 percent set. This would indicate that the spiraling action of the closing corolla would likely contribute to perpetuation of the species if previous pollination had failed but would not result in maximum fruit set. Crane (1947) (citing Ustinova 1938) stated that cv. 'Viridis' is entirely self-pollinated while cv. 'Vulgaris' is cross-pollinated 2.6 to 2.9 percent of the time.

As early as 1911, Howard and Howard (1911) concluded that the opportunities for cross-pollination are very great; however, studies on pollination of kenaf have dealt mainly with the effects of cross- pollination between strains, with little attention given to the effect of pollination on total production of seed.

Pollinators:

Jones and Tamargo (1954) concluded that wind is not a factor in kenaf pollen dispersal. A wasp (Campsomeris trifasciata (F.) was observed in the field (in Cuba) throughout the flowering period; however, it visited only the extrafloral nectaries on the seed capsule during most of the flowering season. A wild bee (Examalopsis similis Cresson) and a carpenter bee (Xylocopa cubaecola Lucas) were seen occasionally in kenaf flowers, but their numbers were too small to be of significance. Jones and Tamargo (1954) concluded that the honey bee was by far the most important insect involved in the pollination of kenaf flowers. It visited an average of 1.36 flowers per minute, 20 per foraging trip, and individual flowers were visited by an average of 16.7 (plus or minus)1.8 bees per day. The peak of honey bee visitation was between 11:30 am. and 2 p.m. No indication was given as to the honey bee colony concentration in the area. Jones et al. (1956) recorded a decreasing amount of crossing with increased distance from the plot of marker plants, when five colonies of honey bees were 1 mile away.

No determinations have been made on the effect of pollination on production of kenaf seed. Like its near relative, the cotton plant, kenaf may produce a crop of self-pollinated seed, but possibly at least some cultivars may produce significantly more seed if the flowers are cross- pollinated. This phase in the economics of seed-production should be investigated.

Pollination Recommendations and Practices:

Tamargo and Jones (1954) concluded that the percentage of natural crossing might be greatly increased if compatible cultivars of similar maturity dates were grown where large populations of honey bees were present. Jones and Tamargo (1954) dealing with the same subject, stated that "If the bee population were increased by placing hives of bees around the kenaf field at flowering time, obviously the number of visits per flower could be increased. Likewise the amount of natural crossing could probably be greatly increased."

Other than these rather vague recommendations for placement of colonies of bees in kenaf fields, there are no recommendations for the use of pollinating agents on kenaf.

LITERATURE CITED:

CRANE, J. C.
1947. KENAF - FIBER PLANT RIVAL OF JUTE. Econ. Bot. 1: 334-350.

DUBEY, R. S., and SINGH, S. P.
1968. NOTE ON STIGMA RECEPTIVITY IN KENAF. Indian Jour. Agr. Sci. 38(1): 195 - 197.

HOWARD, A., and HOWARD, G. L. C.
1911. STUDIES IN SOME INDIAN FIBRE PLANTS. II. ON SOME NEW VARIETIES IN HIBISCUS CANNABINUS L. AND HIBISCUS SABDARIFFA L. Indian Dept. Agr. Mem. Bot. Ser. 4: 1 - 36.

JONES, D., PUENTES, C., and SUAREZ, R.
1955. ISOLATION OF KENAF FOR SEED INCREASE. Agron. Jour. 47: 256.

JONES, M. D., and TAMARGO, M. A.
1954. AGENTS CONCERNED WITH NATURAL CROSSING OF KENAF IN CUBA. Agron. Jour. 46: 459 - 462.

KILLINGER, G. B.
1965. KENAF - POTENTIAL PAPER-PULP CROP FOR FLORIDA. Fla. Agr. Expt. Sta. Agr. Res. RPt. 10(2): 4-5.

KILLINGER, G. B.
1967. POTENTIAL USES OF KENAF (HIBISCUS CANNABINUS L.). Soil and Crop Sci. Soc. Fla. Proc. 27: 4-11.

______ 1969. KENAF (HIBISCUS CANNABINUS L. ) A MULTI-USE CROP. Agron. Jour. 61: 734-736.

NESMEYANOVA, A. D.
1968. [SOME DATA ON THE NECTARIES OF THE AMBARY HIBISCUS CANNABINUS (KENAF).] Uzbek. Biol. Zhur. 12(1): 38 - 40. [In Russian, English summary.]

PATE, J. B., SEALE, C. C., and GANGSTAD, E. O.
1954. VARIETAL STUDIES OF KENAF, HIBISCUS CANNABINUS L. IN SOUTH FLORIDA. Agron. Jour. 46 75.

______and JOYNER, J, F.
1958. THE INHERITANCE OF A MALE STERILITY FACTOR IN KENAF, HIBISCUS CANNABINUS L. Agron. Jour. 50: 402.

TAMARGO M. A., and JONES, M. D.
1951. NATURAL CROSS-FERTILIZATION IN KENAF. Agron. Jour. 46: 456 - 459.

USTINOVA E. I.
1938. [CROSS-POLLINATION IN HIBTSCUS CANNABINUS.] Selek. i Semen. 6: 32-33. [In Russian.]

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KIWI
(See "Chinese Gooseberry")

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KOLANUT
Cola spp., family Sterculiaceae

Several species of Cola are cultivated for the kolanut. Purseglove (1969*) listed four cultivated species, but van Eijnatten (1969) stated that only two were of commercial significance: (C. nitida (Vent.) Schott & Endl., which is the main kola of commerce, and C. acuminata (Beauv.) Schott & Endl.). The kolanut is native to Africa, with Nigeria the primary producing country. An estimated 140,000 tons were produced in 1960 mostly in Nigeria. This would indicate that something like one-half million acres were involved. A few hundred tons are exported to the United States, where they are used in the preparation of beverages and in pharmaceuticals. In Africa, the kolanut is chewed for its alkaloid properties (caffeine, kolanin, and theobromin), which dispel sleep, thirst, and hunger. There seems to be a slight preference for white kolanuts over red ones.

For the above and subsequent discussion, see van Eijnatten (1969) and Russell (1955a, b).

Plant:

The kola tree is a dome-shaped evergreen tree, usually 35 to 50 feet in height. Trees are usually planted from seed, about 20 to 27 feet apart, although vegetative production can be accomplished. Growth of this tropical tree is in flushes. Flowering begins at 6 to 10 years. The fruit matures about 41/2 months after flowering. Full fruit production is reached by the 20th year, and the tree may continue bearing until it is 70 to 100 years old. The main harvest period of nuts extends from October to December, but some nuts may be available throughout the year. The pod is harvested before the nuts are ripe. The follicle is split and the three to six nuts are removed, fermented in heaps for 5 days, washed clean, and stored. They will keep for several months. Average yield is 210 to 250 salable nuts per tree or 12,000 nuts (about 500 pounds) per acre.

Inflorescence:

The fetid kola flowers are in several- to many flowered determinate panicles. The five-sepal, petalless flower is white, with maroon to reddish blotches and streaks emanating from the inner base of the corolla-like perianth. Some trees produce only male flowers, but some hermaphrodite flowers are usually on every tree. Usually, the earliest flowers to develop are male; followed by both male and hermaphrodite flowers intermixed. The hermaphrodite flower is 30 to 40 mm across; the male flower, half to two-thirds the size. The male flower is subspherical, the hermaphrodite one is more oval. The hermaphrodite flower produces pollen that will germinate on a proper agar solution but will not fertilize a stigma, so the flower is basically nonfunctional, and should be considered as a pistillate one.

The hermaphrodite flower opens between 4 and 8 a.m. and is apparently receptive only one day, as the majority wither and drop on the second to the fourth day. Naturally, all male flowers shed. When the flower opens, the anthers dehisce a sticky pollen, which largely remains on the anthers. This would indicate that the kola flower is insect pollinated. No reference was found indicating that kola flowers secrete nectar, but since flies are attracted to the flowers quite probably nectar is secreted.

Pollination Requirements:

The evidence indicates that pollen must be transferred from the staminate or male flowers to the hermaphrodite or basically female flowers. The pollen must be transferred as soon as possible after the flower opens. Many trees, and probably the majority of them, are self- incompatible, in which case the pollen must come from flowers of other appropriate kola trees.

Considering the large number of flowers on a tree that must set fruit to produce an excellent crop, and considering that the pollen must come from other compatible plants and within a limited time period, it becomes evident that pollen must be transported rather freely between trees.

Pollinators:

The pollen of kola trees is not wind transported. Van Eijnatten (1969) said that pollination is probably affected by insects, but indicated that relatively few insects visit the numerous flowers. Purseglove (1968*) stated that the flowers have a fetid odor that attracts flies, which may be the pollinating agent. Cecidomyids, mirids, and ants have also been mentioned (Anonymous 1957). Nothing is said about bee visitation to these flowers. It is of interest that this is a relatively self- sterile crop, and van Eijnatten (1969) stated that, "The low productivity of many kola trees has been a thorn in the flesh of the farmer wherever this crop is cultivated in West Africa." The saturation pollination with one to several honey bee colonies per acre, forcing the bees to forage on what may be a relatively unattractive source of pollen or nectar, might remove that objectionable "thorn in the flesh." It might lift total production to a new plateau or cause a more concentrated set of fruit at a definite period.

Van Eijnatten (1969) stated that controlled pollination, apparently referring to hand pollination, could increase the yield ten- to twentyfold. This should appear to be sufficient incentive for the kolanut industry to explore the utilization of honey bees or other bees in the pollination of this crop.

Pollination Recommendations and Practices:

None.

LITERATURE CITED:

ANONYMOUS.
1957. KOLA POLLINATION STUDIES. In Eed. Dept. Agr. Res., Nigeria, Prog. Rpt. 5, pp. 5-8.

EIJNATTEN, C. L. M. VAN.
1969. KOLANUT. In Ferwerda, E. P., and Wit, E., eds., pp. 289-307 Outlines of Perennial Crop Breeding in the Tropics. H. Veenman and Zonen, N. V. Wageningen, The Netherlands.

RUSSELL, T. A.
1955a. THE KOLA NUT OF WEST AFRICA. World Crops 7: 221 - 225.

______ 1955b. THE KOLA NUT OF NIGERIA AND THE CAMEROONS. Trop. Agr. [Trinidad.] 32: 210 - 241.

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LOQUAT
Eriobotrya japonica (Thunb.) Lindl., family Rosaceae

The loquat is also called Japanese plum, Japanese medlar, and rush orange. It is not grown commercially to any extent for its fruit in the United States (Campbell 1965), but it is a common southern dooryard and ornamental plant. It will do well wherever lemons grow.

Plant:

The loquat is a rather long-lived symmetrical evergreen to 25 feet tall, with oblong, stiff dark-green leaves 8 to 12 inches in length (Bailey 1949*). Condit (1915) recommended that the plants be spaced 12 feet apart in the row, and rows 24 feet apart for commercial production.

The fruit, which ripens in the spring, can be damaged by slightly below freezing temperatures (Mowry et al. 1967*). The 1- to 3-inch pear- shaped fruits, four to 10 per cluster, have three to five seeds, and yellow flesh. They are used fresh or in preserves or jams and in making a delicious jelly (Kennard and Winters 1960*). There are many cultivars in Florida, some trees of which may yield as much as 300 pounds fruit (Campbell 1965).

Inflorescence:

The name "Eriobotrya" (Greek: woolly inflorescence) refers to the profusion of small woolly flowers born in a terminal dry-bracted panicle. Flowering occurs from October to February, sometimes in up to three flushes of blooms in a season. The second one usually sets the most fruit (Chandler 1958*). Blossoms in the northern part of Florida and similar regions seldom bear fruit because of cold injury. Bees visit the blossoms freely for nectar and pollen. A copious quantity of nectar may collect in the open cavity around the ovary, below the base of the anthers. In warmer areas of China, the loquat is reported to be the principal source of surplus honey in November (Pellett 1947*).

There are 10 to 50 small fragrant white flowers in a panicle, only about 12 percent of which develop into fruit. Each flower has five petals, five stigmas, about 20 stamens, and five carpers (fig. 127). Each carper has two ovules; therefore, 10 seeds may develop, although rarely more than three to five do so (Smock 1937, Campbell and Malo 1968). Thinning of fruit may be necessary if the set is too heavy, but usually the set is too light for economic production.

Pollination Requirements:

The pollination requirements seem to vary with cultivars of loquat, but all are benefited by, and some require, cross-pollination. Crescimanno (1958) reported that even individual cultivars vary widely from year to year in the amount of fruit set through self-pollination. He found that bagged blossoms set only 0.0, 16.5, and 1.3 percent; whereas, open blossoms set 4.2, 12.0, and 21.7 percent; and crossed flowers (the last 2 years) set 60 and 55 percent of the blossoms. High temperatures seem to be detrimental to fruit set. This could be the result of a decreased period of stigma receptivity or pollen viability associated with inadequate pollinator activity. Mortensen and Bullard (1968*) reported that cross- pollination was beneficial to all varieties and necessary in some. Kennard and Winters (1960*) also reported that the flowers are self-incompatible, so several trees should be planted close together to assure cross- pollination.

The details of the flowers' period of receptivity is not known, however Singh (1963) found that pollen will remain viable 35 to 45 days at room temperature, 22 months at 0deg C., and 26 months in a deep freeze.

Pollinators:

Nothing is mentioned in the literature about the pollinating agents for loquat. However, honey bees visit the flowers freely and are usually the primary visitors. Presumably, they are satisfactory pollinating agents.

Pollination Recommendations and Practices:

None. Where maximum fruit set is desired, plants should probably be in close proximity and bees should be present in abundance during flowering.

LITERATURE CITED:

CAMPBELL, C. W.
1965. THE WOLFE LOQUAT. Fla. Agr. Expt. Sta. Cir. S-170,6 pp.

____ and MALO, S. E.
1968. THE LOQUAT. Fla. Agr. Ext. Serv., Fruit Crops Fact Sheet 5,2 pp.

CONDIT, I. J.
1915. THE LOQUAT. Calif. Agr. Expt. Sta. Bul. 250: 251-284.

CRESCIMANNO, F. G.
1958. [INVESTIGATIONS ON THE FLORAL BIOLOGY OF THE LOQUAT.] Riv. Orto-florofruttic Ital. 83: 107-120. [In Italian.] Abstract in Plant Breed. 28(4): 821. 1958.

SINGH. S. N.
1963. STUDIES ON THE LONGEVITY OF LOQUAT POLLEN. Trop. Agr. [Ceylon.] 119: 31-36.

SMOCK, R. M.
1937. MORPHOLOGY OF THE FLOWER AND FRUIT OF THE LOQUAT. Hilgardia 10(16): 615-627.

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RASPBERRY
Rubus spp., family Rosaceae

The commercial cultivated raspberries include the red raspberry of Europe (R. idaeus L.), the red (R. strigosus Michx.) and black (R. occidentalis L.) wild raspberries of North America, and the purple raspberry, which was developed here as a cross between R. strigosus and R. Occidentalis (Darrow 1937).

In 1971, the estimated production of raspberries in frozen commercial pack was 28 million pounds, most of which came from Oregon, Washington, and the northern Midwest. This does not include production in home gardens for fresh use or for frozen food lockers. Production ih the above two States from 8,730 acres in 1969 amounted to 39 million pounds valued at $11.2 million (USDA 1971).

Plant:

Raspberry roots may live for years, but the "cane" or stem lives only 2 years. Usually, the cane growth is attained the first year, then the fruit is produced the second year, after which the cane dies. Some kinds produce a fall crop on the terminals of current season canes (Magness et al. 1971). Red and purple raspberry canes may reach a height of 8 feet. They are upright or semierect. Black raspberries, or black caps, have arched canes that reach 4 to 5 feet and form roots at the tips. Hybridization of the species has produced many variations in the growth habits of these plants. The thorns or spines on the stems vary from strong and sharp to scattered weak prickles or none. The leaves are usually deciduous (USDA 1967).

The fruit, a berry, consists of many one-seeded drupelets or carpers on the receptacle. When the fruit is harvested, the receptacle remains on the plant, leaving the fruit as a more or less hollow cap (Bailey 1949*).

Inflorescence:

The raspberry flower is about 1 inch in diameter and has five whitish petals, many stamens inserted on the calyx, and many ovaries, each with a slender terminal style usually remaining on the drupelet. The flowers are mostly bisexual (Eaton et al. 1968).

When the flower opens, the anthers are immature, with the filaments bent over the immature styles (fig. 167). Subsequently, the outer stamens bend back toward the petals and their anthers dehisce. As dehiscence progresses toward the center of the flower, the receptacle expands, the styles grow, and the receptive stigmas appear at their tips; later, the anthers nearest the stigmas dehisce, and, if cross-pollination has not already been brought about by insects, some selfing may result. The degree of such selfing seems to vary with species and cultivar, but most of them are largely self-sterile.

A day or so after the flower opens, the petals begin to shed. Flowering on a plant may occur over 1 to 3 weeks. Nectar is secreted abundantly by a fleshy ring on the margin of the receptacle (inside the ring of stamens) (Knuth 1908*, p.351). The rich and copious nectar (13 mg per flower) (Haragsimova-Neprasova 1960, Petkov 1963) as well as the pollen are highly attractive to insects. Commercial production of a high quality, much sought after raspberry honey occurs in some Northern States and Canada.

[gfx] FIGURE 167. - Longitudinal section of 'Willamette' raspberry flower, x 10.

Pollination Requirements:

Wellington (1913) and Hardy (1931) concluded that the raspberry is self-fertile, and that the pollen fertilizes the stigma before the flower is open. Other research has shown that they reached erroneous conclusions. Johnston (1929) showed that only 16 to 70 percent of the flowers produced berries when insects were excluded, as compared to 64 to 98 percent that set when the blossoms were exposed to pollinating insects. Couston (1963, 1966) compared production of a few plants caged to exclude pollinating insects with plants exposed to insect visitation. Fruit developed on plants of both treatments, but on the caged plants the size of the berries was so small (half the size of those on the open plants) and the volume of fruit produced was so low (one-third less) that it was not worth harvesting commercially. When the 'Malling Jewel' cv. was caged against insects, it produced almost no berries, but plants caged with a colony of honey bees yielded better than those in the open. Couston concluded that raspberries can be pollinated by honey bees alone, without other insects if necessary.

Shanks (1969) used cages over raspberries with and without colonies of honey bees enclosed. He found that the fruits had 71 to 82 percent fewer drupelets in the absence of bees, and that wind was not a factor in raspberry pollination. The fruit that set in the beeless cages was distinguished by a tuft of unpollinated pistils on the end of each berry. He considered the honey bee of primary importance in the pollination of raspberries in Washington. Allen (1937) stated, without supporting data, that raspberry bushes ". . . bear but little fruit unless there are some bees in the neighborhood." Likewise, Smith and Bradt (19678) stated without supporting data, that raspberries and blackberries are self-fruitful but require bees for pollen transfer.

In a well-conducted test, Eaton et al. (1968) showed the value of repeated bee visits in producing more and larger red raspberries. They emasculated the flowers, treated the stigmas to different pollen applications, and recorded the results in terms of fruit set and drupelets per fruit. Their results are shown in table 15.

[gfx] fix table 15:

TABLE 15. - Value of repeated bee visits in producing red raspberries __________________________________________________________ Treatments ____________________________ Fruit set and size 11 22 33 44 55 __________________________________________________________ Mean number of fruits set of 5 flowers 1.0 2.7 2.8 3.8 4.2 Mean number of drupelets per fruit 5.3 21.5 35.0 38.3 40.0 __________________________________________________________ 1No pollen applied to stigma. 2 Pollen applied once, immediately after emasculation. 3 Treated same as treatment 2, then poHen was applied again on the following day. 4 Treated same as treatment 3, then pollen was applied again on the 3d day. 5 Treated Same as treatment 4, then pollen was applied again on the 4th day.

The results showed that for the largest number of berries with the most drupelets, each flower should be repeatedly visited by bees for at least 4 days.

Pollinators:

Honey bees are the best pollinating agents of raspberries. Because honey bees and raspberries are mutually benefited, these insects should be given major consideration as pollinators of raspberries.

Pollination Recommendations and Practices:

None of the research workers who have studied the pollination requirements of raspberries have recommended that steps be taken to increase the pollinator population on the raspberry since Hooper (1913) made the general statement that raspberries need insect pollination. He recommended one colony for each 2 acres. The evidence is plain that the plant requires or at least is greatly benefited by such pollination. Where the crop is grown commercially with its vast numbers of blossoms calling for insect transfer of pollen from anthers to stigmas, whether on the same flower, flowers of the same plant, or between plants, bees should be supplied to the plantings. The grower is interested in the largest possible berries as well as maximum production. This can only be obtained with ample insect pollinators.

No studies have been made on the number of bee visitors per flower that result in maximum pollination, although Eaton et al. (1968) showed that the flowers should be visited for at least 4 days. The anthers are not all open at the same time nor are all of the stigmas receptive at once. Thus, repeated bee visits are quite probably necessary if all of the ovules are to be cross-pollinated and a well-formed berry is to be harvested. Until real evidence is available, one can only compare bee activity and floral structure of other plants in estimating the bee activity desired. By this method, a desired bee population of about one bee visitor for each 100 open blossoms would appear logical. The colonies per acre necessary to supply this visitation would depend on the acreage of berries involved, competing plants, colony strength, and many other factors. The importance and value of the bees is so great that quite likely several colonies per acre would be justified.

LITERATURE CITED:

ALLEN, M. Y.
1937. EUROPEAN BEE PLANTS. 148 pp. Bee Kingdom League, Alexandria, Egypt.

COUSTON, R.
1963. THE INFLUENCE OF INSECT POLLINATION ON RASPBERRIES. Scot. Beekeeper 40: 196-197.

______ 1966. EXPERIMENTS ON THE INFLUENCE OF INSECT POLLINATION ON SOFT FRUITS. Scot. Beekeeper 43(3): 39-40, (5): 90-92.

DARROW, G. M.
1937. BLACKBERRY AND RASPBERRY IMPROVEMENT. U.S. Dept. Agr. Yearbook 1937: 496-533.

EATON, G. W., DAUBENY, H. A., and NORMAN, R. C.
1968. POLLINATION TECHNIQUES FOR RED RASPBERRY BREEDING PROGRAMS. Canad. Jour. Plant Sci. 48(3): 342-344.

HARAGSIMOVA-NEPRASOVA, L.
1960. [MEASUREMENT OF NECTAR SECRETION IN PLANTS.] Ved. Prace Vyzkum. Ustav. vcelar CSAZV 2: 63-79. [ln Czech., English and other summaries.]

HARDY, M. B.
1931. SELF AND CROSS FERTILITY OF RED RASPBERRY VARIETIES. Amer. Soc. Hort. Sci. Proc. 28: 118-121.

HOOPER, C. H.
1913. THE POLLINATION AND SETTING OF FRUIT BLOSSOMS AND THEIR INSECT VISITORS. Roy. Hort. soc. Jour. 38: 238-248.

JOHNSTON, S.
1929. INSECTS AID FRUIT SETTING OF RASPBERRY. Mich. Agr. Expt. Sta. Quart. Bul. 11(3): 105-106.

MAGNESS, J. R., MARKLE, G. M., and COMPTON, C. C.
1971. FOOD AND FEED CROPS OF THE UNITED STATES - A DESCRIPTIVE LIST CLASSIFIED ACCORDING TO POTENTIALS FOR PESTICIDE RESIDUE. N.J. Agr. Expt. Sta. luterregion. Res. Proj. lR-4, IR Bul. 1, 255 pp.

PETKOV, V. [G.]
1963. [NECTAR PRODUCTION IN CULTIVATED RASPBERRY.] Sell Nauk. 2: 201-207. [In Bulgarian, Russian and English summaries.] AA-495/66.

SHANKS, C. H., JR.
1969. POLLINATION OF RASPBERRIES BY HONEYBEES. Jour. Apic. Res. 8: 19-21. UNITED STATES DEPARTMENT OF AGRICULTURE. 1967. GROWING RASPBERRIES. U.S. Dept. Agr. Farmers' Bul. 2165, 14 pp.

______ 1971. FRUITS. PART 1 NON-CITRUS BY STATES, 1969 - 7O, PRODUCTION USE VALUE. U.S. Dept. Agr. Statis. Rptg. Serv. CRB, FRNT 4-1 (5-71), 22 PP.

WELLINGTON, R. [A.]
1913. RASPBERRY BREEDING. Amer. Soc. Hort. Sci. Proc. 10th Ann. Mtg., pp. 155-159.

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STRAWBERRY
Fragaria X ananassa Duch, family Rosaceae

The estimated acreage of U S. strawberries in 1971 was 51,000, and the crop was valued at $116 million.

Oregon was the leading grower of strawberries, with 11,000 acres, followed by California (8,300 acres), Michigan (5,600), Washington (4,100 acres), and North Carolina (1,900 acres). Numerous other States produced more than 1,000 acres. California led with 151,500 tons, followed by Oregon (41,650 tons), Washington (13,350 tons), Michigan (12,300 tons), and Florida (7,600 tons). The numerous cultivars have changed rapidly over the last few years (Scott 1971). Much of the material herein is drawn from the excellent reference by Darrow (1966).

Plant:

The strawberry plant is a stemless, low creeping, and usually perennial herb that may live for many years, although it is sometimes grown as an annual in the South (Shoemaker 1955). Some cultivars are evergreen and others tend to be deciduous, depending upon the area in which they are grown. The trifoliate leaves form a blanket cover of the ground from a few inches to 2 feet deep, which shelters the fruit. The creeping runners occasionally produce roots and inflorescences at the leaf bases.

The ripe fruit is 1 to 2 inches long and light red to dark red when ripe. It is an ovoid aggregate of achenes or one-seeded fruitless around a receptacle that accumulates sugars and vitamins and ripens like a true, fleshy fruit. Each achene contains a single ovule and can therefore be considered an individual unit. Yet, if the stigma of the achene is not pollinated or if it is removed soon after pollination, there is no growth on the receptacle. The weight of the strawberry is roughly proportional to the number of fertilized ovules (Nitsch 195O).

Reproduction is almost exclusively with rooted runners, even though the seeds are viable.

Inflorescence:

The strawberry flower cluster is a series of double-branching parts bearing a flower in the crotch of each branch. The flower in the first crotch is termed the primary flower, the two in the next two crotches are termed secondary flowers, the next four are tertiary flowers, the next eight are the quarternary, and the next 16, if they develop, are the quinary flowers. The primary flower opens first and usually produces the largest berry (fig. 175) (Shoemaker 1955).

The individual flower is whitish (fig. 176), 1 to 1l/2 inches across, and usually composed of about 5 to 10 green sepals, five oval petals, numerous styles, and two to three dozen stamens arranged in three whorls. When the stamens contain viable pollen, they are a deep gold. Nectar is secreted by the receptacle and held at the base of the stamens next to the outer row of pistils.

The flowers of all current commercial cultivars are hermaphrodite. Clones that are only staminate or only pistillate may appear in the wild or in some seedling populations (fig. 177). The hermaphrodite flowers set fruit somewhat in proportion to the extent of pistillateness, that is, the higher the percentage of pistillate flowers, the more fruit the plant produces.

The stigmas are receptive before pollen of the same flower is available, which encourages cross-pollination. Sometimes, flowers that have pollen-laden anthers appear to set fruit far better when cross- pollinated than when fertilized with their own pollen. The pollen is mature before the anthers dehisce, but dehiscence does not occur until after the flower opens and the anthers dry a short while. This causes them to dehisce under tension so that the pollen is thrown onto some of the pistils. It can remain viable for several days, but some flowers are dried and shrunken on the second day after opening (Connor 1970); therefore, it is no longer of value to the flower. No complete self-incompatibility exists in present-day cultivars.

The fruit of the first blossom to open is referred to as the primary berry and is usually the largest. The second flower to open is the secondary flower, and the fruit it produces is usually second in size. Fruits from later flowers are usually smallest. Darrow (1966) stated that Valleau (1918) found 382 seeds in primary berries, and 224, 151, and 92 seeds in the succeeding berries. Gardner (1923) recorded 518 pistils on one primary flower but only 83 pistils for the last flowers of the plant under his study. There can be less but never more achenes (fruitless) than there are pistils.

[gfx] FIGURE 175. - Cluster of 'Midway' strawberries in different stages of developement.
FIGURE 176. - Strawberry blossoms, buds, and leaves.
FIGURE 177. - Longitudinal section of 'Tioga' strawberry, x 7, with individual achene and style, x 35.

Pollination Requirements:

Flowers without stamens were common in earlier cultivars, and no fruit setting resulted unless pollen was brought from staminate flowers (Darrow 1927, 1937). Continued breeding and selecting has resulted in the hermaphrodite flowers in all commercial cultivars. However, hermaphrodite flowers may not be completely self-fertilizing. The stamens are so placed that when they crack open they readily scatter pollen onto many, but not necessarily all, of the pistils. Pollination of all of the pistils of a flower is necessary for maximum berry size. If all pistils are fertilized, a perfectly shaped berry should develop. If few are fertilized, an irregularly shaped berry or "nubbin," sometimes only one- fifth the size of well-fertilized berries, will develop.

Allen and Gaede (1963) studied fruit-setting of 'Shasta' strawberries in the greenhouse and showed that plants caged and undisturbed by man, insects, or breezes set no fruit; those uncaged and undisturbed set 20 percent; those uncaged but receiving wind from a fan over them set 77 percent; whereas those that were caged, but brush pollinated daily, set 97 percent of the flowers. This finding indicated that the plants alone set few fruits, and wind has some effect, but insects may be more important than wind as pollinating agents. Couston (1966) also noted that malformation of berries was greater when adverse weather occurred at flowering time. He also obtained more number one berries from exposed plants than from plants caged to prevent insect visitation, indicating that insect pollination increased production.

Free (1968a) compared production of plots caged to exclude pollinating insects, plots caged with a colony of honey bees in each cage, and open plots. The cages without bees yielded the lowest percentage set, 55 percent as against 65.5 percent for the cage with bees. They also yielded the smallest berries, 6.7 g per berry in the cage without bees as against 8.3 and 8.4 g in the cages with bees and open plots, and the highest percentage of malformed berries, 48.6 percent in the no bee cages, 20.7 percent in the bee cage, and 15.4 percent in the open plots. Howitt et al. (1965) also associated strawberry fruit deformity with faulty pollination. Hughes (1961) noted that excluding pollinating insects resulted in decreased yield and malformed fruit. Kronenberg (1959) and Kronenberg et al. (1959) listed insufficient pollination by bees as one cause of poor fruit set.

Darrow (1966) stated that when the first flowers of perfect- flowered cultivars open and set well, but later flowers only partially set or do not set at all, natural sterility is the primary cause. However, he said that if the first flowers develop into nubbins, and yet later flowers produce good berries, the poor development is probably due to inadequate pollination.

Connor and Martin (1973) made the interesting observation that stamen height ranged from 2.5 mm in 'Surecrop' to 5.2 mm in 'Early Midway', and the flowers with the shorter stamens benefit most from insect pollination. Based upon their studies of 11 cultivars, they reported the following: "Self-pollination is responsible for development of 53 percent of the achenes; wind motion increased this development to 67 percent and insect pollination increased it to 91 percent."

Pollinators:

Many types of insects visit strawberry flowers, including flies, beetles, thrips, butterflies, and various bees; however, only the bees are of real consequence in transferring pollen effectively without injuring the flower parts. If wild bees are not plentiful so that the flower obtains the 16 to 25 bee visits recommended by Skrebtsova (1957), honey bees can be provided. Honey bees show preference for some cultivars over others, and they are not too strongly attracted to strawberries. However, this can be overcome with saturation pollination, or overstocking the area with colonies so the competing nectar and pollen are removed (fig. 178).

Although the strawberry blossom produces nectar and usually pollen, it is not overly attractive to honey bees. Also, different cultivars are visited by bees to different degrees, but none have been reported to be highly attractive. Free (1968a) stated that honey bee visits tend to be limited to good weather. Allen (1937) stated that when bees visited the strawberry blossoms, fruit production was increased, but the blossoms were not as popular with bees as one might wish.

In studying the activity of honey bees on strawberries, Free (1968b) found that although bees sometimes landed on the petals of a flower and approached the nectary from the side, they nearly always proceeded to walk over the stigmas. Some bees collected mostly nectar but also some pollen; however, some bees collected pollen deliberately. He stated, "Such bees either walked round the ring of anthers and scrabbled for pollen while doing so, or stood on the central stigmas and pivoted their heads and parts of their thoraxes over the ring of anthers. Some bees scrabbling for pollen also collected nectar." In either case, honey bees in sufficient numbers should be effective pollinators.

Skrebtsova (1957) studied visitation of strawberry flowers by honey bees. She noted that the bees showed preference for some cultivars over others, but concluded that each flower should receive at least 16 to 20 visits. More visits resulted in heavier berries; 16 to 20 visits resulted in berries weighing 5.36 g, and 21 to 25 visits produced berries that averaged 8.13 g. Flowers pollinated at the most receptive time, the time of fullest development of the reproduction organs, produced berries 13.3 to 58.3 percent heavier than those pollinated before or after this time. Later, Skrebtsova (1958) recommended saturated pollination by bees to produce the maximum crop of highest quality berries.

Moore (1964) noted that strawberry flowers are receptive up to 7 days after opening. Darrow (1966) said 10 days in cool weather, but the number of seeds per berry was reduced in late-pollinated flowers. As previously stated, Connor (1970) reported that many flowers were dried and shrunken on the second day after opening. The best time for pollination seems to be during the first 1 to 4 days after the flower is open. Darrow (1966) noted that reaction to pollination is rapid, within 24 to 48 hours the petals fall and the pistils dry up. Connor (1970) did not distinguish between pollinated and other flowers.

Fletcher (1917) stated that 90 percent of the pollination of strawberries was performed by insects and that honey bees accounted for 90 percent of this activity. Lounsberry (1930) stated that when bee forage was marginal, the bees worked strawberry blossoms feverishly. In Russia, Shashkina (1950) concluded that wind was not a good pollen vector but that flies were the principal vectors in the Moscow area.

Mommers (1961) showed that honey bees increased production in the greenhouse. This was supported by Bonfante (1970). Muttoo (1952) stated that location of an apiary near a strawberry plot increased the average production of berries from 840 to 1,225 pounds per acre. Petkov (1963) stated that only 31 to 39 percent of flowers isolated from bees developed fruit compared to 55 to 60 percent of those freely visited by pollinating insects. Furthermore, the isolated flowers developed 60 to 65 percent culls compared to 14 to 17 percent culls from bee-visited flowers. The average weight of fruit from the isolated flowers was only a third of that from the bee-visited flowers.

Petkov (1965) stated that over a 4-year period of observation bees accounted for 50 to 78 percent of the flower visitors (in Bulgaria). Pammel (1930, p. 922) noted that the flowers at Ames, Iowa, were visited by honey bees and by species of Halictus.

Moore (1969) studied the effects of caging and bees on strawberries over a 4-year period. He concluded that caging, which reduced yields 41, 32, 59, and 71 percent, respectively, for the years 1965-68, was " . . . due to incomplete pollination as a result of excluding insects." While pollinating insects were shown to be unessential for fruit set, the maximum yields and fruit size are only realized under conditions of adequate and active insect pollinators. Anderson (1969) cited numerous references relating to strawberry pollination.

[gfx] FIGURE 178. - Honey bee collecting pollen from strawberry blossom. In the process thorough pollination of the flower is assured.

Pollination Recommendations and Practices:

Free (1968a) discouraged the rental of bees " . . . unless the plantation is large." Darrow (1966) did not consider supplemental pollination, although he showed the need for insect visitation. Mommers (1961) recommended the use of bees on strawberries in greenhouses. Moore (1969) stated that "growers may someday have to provide colonies of honey bees for their plantations." Jaycox (1970) recommended one strong colony per 2 acres, with the bees in two or more groups on opposite sides of 10- to 50-acre fields. Unfortunately, as Connor (1970) pointed out, no specialist can wisely point to a strawberry field and state that the field is either well pollinated or needs additional pollination activity.

In general, strawberry growers do not take steps to provide additional pollination, nor even give much consideration to the local pollinator population in the field, although the evidence shows that visitation by pollinating insects is highly beneficial. The acreage devoted to strawberries on most farms is small compared to the foraging range of bees from an apiary, although some fields of 200 acres are in this crop. Thus, many acres of plants around a strawberry field can be more attractive to honey bees than the strawberry flowers. To overcome this competition would call for saturation pollination, or the placement of many colonies for each acre of strawberries, possibly 5 to 10 or even more. For a commercial grower who desires the maximum in perfect berries as well as in volume, saturation pollination should be profitable.

LITERATURE CITED:

ALLEN, M. Y. 937.
1937. EUROPEAN BEE PLANTS. 148 pp. The Bee Kingdom League, Alexandria, Egypt.

ALLEN, W. W., and GAEDE, S. E.
1963. STRAWBERRY POLLINATION. Jour. Econ. Ent. 56: 823-825.

ANDERSON, W.
1969. THE STRAWBERRY, A WORLD BIBLIOGRAPHY. 731 pp. Scarecrow Press Inc., Metuchen, N.J.

BONFANTE, S.
1970. [POLLINATION OF THE STRAWBERRY.] Conv. Naz. della Fragola, Atti. Cesena (Italy) 4: 291-296. [In Italian.]

CONNOR, L. J.
1970. STUDIES OF STRAWBERRY POLLINATION IN MICHIGAN. In The Indispensable Pollinators, Ark. Agr. Ext. Serv. Misc. Pub. 127, pp. 157-162.

______and MARTIN, E. C.
1973. COMPONENTS OF POLLINATION OF COMMERCIAL STRAWBERRIES IN MICHIGAN. HortScience 8: 304-306.

COUSTON, R.
1937. STRAWBERRY IMPROVEMENT U.S. Dept. Agr. Yearbook 1937: 445-495.

DARROW, G. M.
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