August 11, 2008

Movento� (spirotetramat) insecticide from Bayer CropScience received EPA registration the end of June for the control of sucking insect pests on all pome and stone fruits. It is a systemic foliar insecticide that belongs to the tetramic acid chemical class (same class as Envidor�) and is classified as a lipid biosynthesis inhibitor. Movento is active by ingestion against the immature stages of aphids, scale, and pear psylla, and also has impact on exposed female adults by reducing fecundity and survival of offspring. Upon penetration of the leaf cuticle, Movento exhibits “2-way systemicity” by moving to all areas of the plant, including new shoot, leaf and root tissues. Formulated as a 2SC, rate of application is 6-9 fl oz per acre, with a seasonal maximum of 15.3 fl oz per acre on stone fruits and 25 fl oz per acre on pome fruits. Movento should not be applied prior to petal fall in order for sufficient leaf tissue to be present for uptake and translocation. In addition, Movento must be tank-mixed with a spray adjuvant/additive having spreading and penetrating properties to maximize leaf uptake and systemicity of the product within treated plants. However, the use of Induce� adjuvant in combination with Movento is prohibited on pome and stone fruits when fruits are present due to adverse plant compatibility. Restrictions include a 24-hour REI (restricted-entry interval) and a PHI (preharvest interval) of 7 days.

Tufted apple bud moth second generation egg hatch  is estimated at 23% complete through August 10, based on an accumulation of 2379 degree days (DD) since biofix of first brood moths on May 4 at the WVU-KTFREC.  Development is about 2 days behind last year based on DD accumulations since biofix through August 10.  The end of last week was the ideal time to initiate applications of Lannate plus an organophosphate insecticide [Azinphos-methyl (Guthion), Imidan]. Applications of Altacor, Delegate, Intrepid, Proclaim, Rimon, or SpinTor should be initiated this week. See the July 28th issue of this newsletter for more information on materials and application timing for second generation control.

Codling moth second generation egg hatch is estimated to be 92% complete through August 10, based on an accumulation of 1934 DD since biofix of first brood moths on May 2.  Third generation egg hatch is predicted to begin on August 20.   Insecticides should be applied for third generation control in those orchards where the pheromone trap capture exceeds 5 moths/trap/week. Spray timing for control, based on DD accumulations after biofix, depends on the material selected. If using Rimon, Intrepid, Assail, Calypso, Cyd-X or Carpovirusine, initiate control at 2160 DD after biofix (1% egg hatch, estimated on August 20). If using Altacor, Delegate, Avaunt, Azinphos-methyl (Guthion), Imidan or pyrethroids, initiate control at 2260 DD after biofix (5% egg hatch, estimated on August 25). An initial spray of any material should be followed by a second complete application in about 10-14 days (7-10 days for Cyd-X or Carpovirusine), or up to three additional alternate-row-middle applications 5-7 days apart (3-5 days apart for Cyd-X or Carpovirusine), if needed based on pheromone trap capture, proximity to harvest, and warm temperatures that favor continued mating and egg-laying. 

Oriental fruit moth third generation egg hatch is estimated at 78% complete on peach, based on an accumulation of 2687 DD since biofix on April 10.  Egg hatch is most likely lagging behind a little on apple due to slower development on this fruit crop.  It is important to remember that third generation adults that emerge in peach orchards will fly to adjacent apple orchards to deposit fourth generation eggs if peach fruits have been harvested.  Therefore, an apple orchard that is clean at this point could sustain late season fruit injury if adjacent to an infested peach orchard.  Because there is typically overlap between the third and fourth generations, the best policy for the remainder of the season is to base the need for treatment on pheromone trap capture.  Initiate insecticide applications about 7 days after exceeding a trap threshold of 10 moths/trap/week, and maintain spray intervals on a 2 week (complete) or 5-7 day (alternate-row-middle) schedule for as long as this condition continues.  Control options on peach [days to harvest] include Delegate [14, (1 on nectarine)], Imidan [14], Ambush [14], Asana [14], Pounce [14], Proaxis [14], Warrior [14], Altacor [10], Intrepid [7], Baythroid (7), Lannate [4, (1 on nectarine)], and carbaryl (Sevin) [3].  Control options on apple include Calypso [30], Asana [21], Battalion [21], Decis [21], Proaxis [21], Warrior [21], Altacor [14], Azinphos-methyl (Guthion) [14], Intrepid [14], Avaunt [14], Danitol [14], Rimon [14}, Assail [7], Baythroid [7], Delegate [7], and Imidan [7].  In addition, CheckMate OFM-F sprayable pheromone [0] may be applied on both apple and peach to provide up to 4 weeks of adult control through mating disruption.

White apple leafhopper second generation nymphs will soon begin to appear on the  undersides of apple leaves.  These may be accompanied by third generation (second generation on apple) nymphs of rose leafhopper in some orchards.  Young nymphs of both leafhopper species appear identical, but older nymphs of rose leafhopper can be differentiated by their spotted appearance (black spots on the back).  Nymphs of both species will reach the adult stage during the harvest period and, if abundant, can become a nuisance to pickers.  In addition, excretion of honeydew from high populations can result in sooty mold deposits on fruit.  Examine the undersides of 10 older leaves per tree on 5-10 trees per block and determine the average number of nymphs per leaf (both species combined).  To prevent economic impact from leafhopper feeding, an average of 3 nymphs per leaf is recommended as an action threshold.  An average of 1 nymph per leaf is recommended as an action threshold where the nuisance to pickers from adults is a concern during harvest.  Recommended materials for control include Lannate, Vydate, Provado, Actara, Assail, Calypso, Clutch, and Avaunt.

PHEROMONE TRAP COUNTS
WEST VIRGINIA UNIVERSITY KTFREC

RBLR = Redbanded leafroller; STLM = Spotted tentiform leafminer; OFM = Oriental fruit moth; CM = Codling moth; TABM = Tufted apple bud moth; DWB = Dogwood borer; LPTB = Lesser peach tree borer; PTB = Peach tree borer; AM = Apple maggot.

PLANT PATHOLOGY

Infection periods and general disease update. We’ve recorded two additional infection periods since the last Orchard Monitor on July 28, 2008. Our disease pressure has been low to moderate for the past two weeks, with most locations receiving adequate rain. Infection periods have not been exceedingly lengthy since July 23-24. On those dates, we had leaf wetting for 31 hours at 68� F with 2.12 inches of rain. This was a "wash off" event, resulting in significant loss of fungicide protection on fruit surfaces. On July 30, we had leaf wetting for 11 hours at 71� F with 0.03 inches of rain. On August 2, we received 0.75 inches of rain and 8 hours of wetting at 67� F. These most recent infection periods are favorable for the development of apple summer diseases. Total rainfall for August to date is 1.01 inches (average for the month is 3.9 inches).

It’s an Election Year so don’t forget the "October Surprise". Control failures with sooty blotch and flyspeck on apple occur either because of poor spray coverage during the latter part of the growing season or because trees were left unprotected through more than 270 hr of accumulated wetting during the preharvest interval. Because fungicide protection on fruit is exhausted after 2 inches of rain, fungicide sprays may be needed in late August and September if heavy rains occur with more than 25 days remaining before fruit will be harvested. Twenty-five days is a "worst-case" scenario, based on experience, for accumulating 270 wetting hours. Maintaining fungicide coverage at normal, extended intervals will protect apple fruit from summer diseases as long as we have a dry weather pattern; in a wet weather pattern spray intervals should be shortened and fungicide rates increased.

Table 1. Dates and conditions for infection periods at the WVU - KTFREC, 2008.

HORTICULTURE

Fruit cracking.  You may use ProVide 10 SG or ProVide (a mixture of GA4 and 7) to reduce fruit cracking by influencing cell wall strength or elasticity. For 'Stayman', apply ProVide (GA4 +7) or ProVide 10 SG in 3 to 6 consecutive sprays at 2- to 3-week intervals beginning 2 to 3 weeks before fruit cracking is anticipated to occur. In Virginia, the first spray is usually put on in mid June to early July. Apply ProVide 10 SG at the rate of 100 to 200 grams (3.5 to 7.0 oz) per acre per application and enough water should be used to wet the fruit (100 to 200 gallons per acre). Addition of Silwet L-77 or other nonionic surfactants at 0.1% (13 oz/100 gallons) will improve absorption of ProVide (GA4 +7) or ProVide 10 SG by fruit.

Pre-harvest fruit drop. Fruitone (NAA) and ReTain (AVG) are two registered compounds that can reduce preharvest drop. They have different modes of action in reducing fruit drop. ReTain can reduce biosynthesis of abscission hormone ethylene and therefore reduces fruit drop. However, fruit maturity and harvest date will be significantly delayed. ReTain can not effectively reduce preharvest fruit drop in some apple varieties such as 'Golden Delicious', 'McIntosh', and 'York', etc. in some years. ReTain is applied at 1 pouch (333 grams or 11.7 oz)/100 gallons water at 2 to 4 weeks before anticipated harvest. Addition of surfactant such as Silwet L-77, or Regulaid at 0.05 to 0.1% will improve the absorption of ReTain.

NAA, a synthetic auxin, reduces pre-harvest fruit drop by directly inhibiting expression of genes related to fruit drop. It is usually applied at 10 to 20 ppm (4 to 8 oz/100 gallons water) 1 week before the first fruit drop (about 2-3 weeks before optimum harvest). However, NAA usually increases fruit ethylene production and enhances fruit softening. NAA-treated fruit cannot store too long. In addition, the effect of NAA in reducing preharvest fruit drop only sustains about 7 to 10 days. It is too short for some apple varieties such as 'Delicious'.

In the last three years, we found that the combination of ReTain and NAA more effectively reduces preharvest drop than does ReTain or NAA alone. Furthermore, we found that ReTain and NAA synergistically reduce preharvest fruit drop because they synergistically inhibit expression of a gene related to fruit abscission. At the same time, ReTain reduces NAA-induced fruit ethylene production and thus maintains fruit firmness. The fruit treated by the combination of ReTain and NAA is as firm as those treated by AVG alone. Apple fruit treated with the combination of ReTain and NAA ripen at the same time as untreated control fruit. The combination of ReTain and NAA can hold apple fruit on the tree for an additional 2 to 3 weeks while maintaining fruit quality. Therefore, apple harvest season can be extended for more than 2 weeks.  Timing of application of ReTain and NAA: ReTain is applied at 1 pouch (333 grams or 11.7 oz)/100 gallons water 2 to 4 weeks before anticipated harvest date of untreated control fruit; NAA is applied at 10 to 20 ppm (4 to 8 oz/100 gallons water) 2 weeks before anticipated harvest date of untreated control fruit.

In terms of benefit, NAA or ReTain alone usually can reduce about 10% pre-harvest fruit drop, while the combination of NAA and ReTain can reduce an additional 10% fruit drop. The yields for NAA- or ReTain-treated apple trees and the combination-treated apple trees are 660 bushels and 720 bushels per acre, respectively, if the yield for untreated control apples is about 600 bushels per acre. For fresh 'Red Delicious' apples, it may increase several hundred dollars per acre if the apple price is around $10 to 14. In addition, yield will increase another 5 to 14% if you harvest them 1 or 2 weeks past the normal harvest date because fruit will increase in weight 5 to 7% per week.

Stimulation of coloring and ripening of apple.  Ethrel can improve fruit color and stimulate ripening for early fresh market if used properly. However, it also can cause severe fruit drop and the fruit can not store too long.  So, a combination of ethrel at 200 to 250 ppm (0.8 to 1 pt per 100 gallons) and NAA at 10 to 20 ppm or ReTain will stimulate fruit ripening, improve fruit color and reduce fruit drop. Use ethrel 1 to 2 weeks before normal picking time. Do not spray ethrel when temperature is higher than 90 ^oF.

Delaying apple fruit ripening.  ReTain (AVG) can effectively delay apple fruit ripening, thereby extending harvest season. ReTain is applied at 1 pouch (333 grams or 11.7 oz)/100 gallons water 2 to 4 weeks before anticipated harvest. Addition of surfactant such as Silwet L-77, or Regulaid at 0.05 to 0.1% will improve the absorption of ReTain. 

Sunburn.  Sunburn may be a problem for some apple orchards. Sunburn is caused by heat stress and solar radiation. The temperature of the surface of the fruit can be as much as 32�F (18�C) above air temperatures when the fruit is exposed to solar radiation and 14 to 16�F (8 to 9�C) warmer than the shaded side of the fruit. The transpiration or evaporation of water from the apple fruit helps to cool the fruit while it is attached to the tree. Sunburn may happen when the fruit surface reaches 115 to 120 �F (46 to 49 �C). It has been reported in Washington State and Chile that compounds such as Vaporgard, Surround, Raynox, and Sunshield can reduce sunburn, but evaporative cooling (overhead sprinkling) or shading nets are more effective in reducing sunburn than compounds they tested. (Dr. Rongcai Yuan, Virginia Tech Extension Horticulturist).

READ THE LABEL CAREFULLY AND USE THE CHEMICALS IN ACCORDANCE WITH LABEL CAUTIONS, WARNING AND DIRECTIONS. REQUEST A MATERIAL SAFETY DATA SHEET (MSDS) FROM THE MANUFACTURER FOR EACH PRODUCT YOU USE.

The West Virginia University Cooperative Extension Service, U.S. Department of Agriculture, West Virginia County
Boards of Education and County Commissions Cooperating.  Equal Opportunity / Affirmative Action Institution