SPECIES: Euphorbia esula

AUTHORSHIP AND CITATION:

Simonin, Kevin A. 2000. Euphorbia esula. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

ABBREVIATION:

EUPESU

SYNONYMS:

No entry

NRCS PLANT CODE [101]:

EUES
EUESE
EUESO
EUESU

COMMON NAMES:

leafy spurge

TAXONOMY:

The currently accepted name of leafy spurge is Euphorbia esula L. (Euphorbiaceae) [35,49,55]. Varieties include [49]:

Euphorbia esula var. esula L.
Euphorbia esula var. orientalis Boiss.
Euphorbia esula var. uralensis (Fisch. ex Link) Dorn

LIFE FORM:

Forb 

FEDERAL LEGAL STATUS:

No special status

OTHER STATUS:

Leafy spurge is listed as a noxious weed within [100]:

AK	AZ	CA	CO	HI
IA	ID	KS	MN	MT
ND	NE	NV	OR	SD
UT	WA	WI	WY

GENERAL DISTRIBUTION:

Leafy spurge is a native to Eurasia. It was imported to the United States as a seed impurity around 1827 [105]. In North America, leafy spurge occurs from Alaska east to Nova Scotia and south to Maryland, Indiana, Nebraska, California, and Mexico. It is most common in fields, roadsides, stream valleys, open woodlands, and waste places [35], and is well established in the Northwest [55].  

ECOSYSTEMS [33]:

FRES15 Oak-hickory
FRES17 Elm-ash-cottonwood
FRES18 Maple-beech-birch
FRES19 Aspen-birch
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES25 Larch
FRES26 Lodgepole pine
FRES29 Sagebrush
FRES35 Pinyon-juniper
FRES36 Mountain grasslands
FRES38 Plains grasslands
FRES39 Prairie
FRES40 Desert grasslands
FRES41 Wet grasslands

STATES:

AK	AZ	AR	CA	CO	CT	DE
HI	ID	IL	IN	IA	KS	ME
MD	MA	MI	MN	MS	MO	MT
NE	NV	NJ	NM	NY	ND	OH
OR	PA	SD	UT	VT	VA	WA
WV	WI	WY	DC

AB	BC	MB	NB	NT	NS	ON
PE	PQ	SK	YK

MEXICO

  BLM PHYSIOGRAPHIC REGIONS [9]:

1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands

	Native Prairie	Vegetation dominated by leafy spurge
Native species
** blue grama	31.8 ± 15.7	>2.0 ± 3.7
**obtuse sedge	31.4 ± 12.7	15.0 ± 14.7
** porcupine grass	30.8 ± 11.8	10.2 ± 10.0
* junegrass	>8.0 ± 5.6	4.0 ± 5.8
** little bluestem	9.3 ± 9.3	0
Alien species
** leafy spurge	0	33.0 ± 24.0
** Kentucky bluegrass	0	28.8 ± 25.9
** smooth brome	0	18.8 ± 16.5

**(p < 0.01)
*(p < 0.05)

IMPORTANCE TO LIVESTOCK AND WILDLIFE:

Leafy spurge irritates the mouth and digestive tract of cattle. The milky latex, distributed throughout the plant, is a gastric irritant  [16] that may produce death in cattle [105].  Hereford, Angus, and crossbred calves show no signs of irritation when leafy spurge or potentially harmful chemicals in spurge are applied to skin, lips, mouths, throats, and organs of gastrointestinal tracts.  However, cattle were observed to scour (which causes dehydration and/or death) after ingesting leafy spurge chemicals [51,79].  

The presence of leafy spurge influences foraging behavior of cattle. Cattle prefer foraging in areas without heavy infestations [63]. A leafy spurge-infested area producing 5500 pounds of grass per acre (1000 kg/ha) showed little or no cattle utilization [41].  As of 1994, the grazing area within North Dakota, South Dakota, and Wyoming lost to leafy spurge infestation could have supported 90,000 cows generating 37 million in annual livestock sales [58]. 

PALATABILITY:

Leafy spurge is palatable to domestic goats and domestic sheep [23,50,57]. The degree of use shown by livestock and wildlife species for leafy spurge in several western states is as follows [23]:

	MT	ND	UT	WY
Cattle	poor	poor	poor	poor
Domestic sheep	fair	fair	poor	poor
Horses	poor	poor	poor	poor
Pronghorn	----	poor	poor	----
Elk	poor	----	poor	----
Mule deer	poor	poor	poor	----
White-tailed deer	poor	fair	----	----

Domestic sheep prefer leafy spurge to crested wheatgrass (Agropyron cristatum) during summer months [47].

 

NUTRITIONAL VALUE:

Leafy spurge meets or exceeds the nutrients required by mature domestic sheep and goats for growth and lactation throughout the growing season [31].  No significant (p < 0.05) difference in weight gain occurred between ewes within a leafy spurge-infested pasture and ewes in leafy spurge-free pasture [57], and no negative effects were found in ruminal digestion and metabolism of domestic sheep when leafy spurge comprised 50% of their diet [99]. Leafy spurge exceeds the nutritional requirement levels for lactating 150-pound (68 kg) domestic sheep and for lactating 100-pound (45 kg) Angora goats [50]. 

A nutritional comparison of leafy spurge with alfalfa (Medicago sativa) was made by Fox and others [31]. Leafy spurge had less protein, more phosphorus, and was generally less digestible than alfalfa. Mean percent composition of leafy spurge and alfalfa at various stages of phenological development was:

	Species	Vegetative	Flowering	Mature	Regrowth
Crude protein	leafy spurge	27.3	23.4	19.5	15.6
	alfalfa	32.8	29.2	25.6	22.0
Available crude protein	leafy spurge	22.4	18.4	14.4
	alfalfa	31.8	28.0	24.2	20.2
Phosphorus	leafy spurge	0.53	0.46	0.39	0.32
	alfalfa	0.44	0.38	0.32	0.26
In-vitro dry matter digestibility	leafy spurge	80	73	66	60
	alfalfa	84	79	74	69
Acid-detergent fiber	leafy spurge	17.9	23.2	28.5	33.8
	alfalfa	18.1	21.7	25.3	28.9

At 9% crude protein, leafy spurge hay contains 20% less protein than mixed orchard grass (Dactylus glomerata)-timothy (Phleum pratense) hay [57].

COVER VALUE:

The degree to which leafy spurge provides cover for livestock and wildlife has been rated as follows [23]:

	MT	ND	UT	WY
Pronghorn	------	good	poor	------
Elk	------	------	poor	------
Mule deer	------	good	poor	------
White-tailed deer	------	good	------	------
Small mammals	------	------	fair	poor
Small nongame birds	poor	------	poor	------
Upland game birds	------	------	poor	------

 

VALUE FOR REHABILITATION OF DISTURBED SITES:

No entry

OTHER USES AND VALUES:

With flowers appearing before the prime honey-producing months, leafy spurge provides an early-season food source for honeybees [78].

OTHER MANAGEMENT CONSIDERATIONS:

Leafy spurge sap may induce blistering or severe dermatitis in humans [48].

Control methods:
Recommendations for control of invasive species evolve continually as new information becomes available from scientists and field managers.  The Fire Effects Information System focuses mainly on interactions of invasive species with fire.  This section summarizes current information on methods of control, but it is not a comprehensive evaluation.  Managers interested in the most up-to-date information on effective, long-term control can contact the National Resource Conservation Service office in their area (http://offices.usda.gov/scripts/ndISAPI.dll/oip_public/USA_map) or their local agricultural or horticultural extension agent (http://www.reeusda.gov/1700/statepartners/usa.htm). 

Biological control:
Concerns for non-target herbicide exposure resulting from chemical control of leafy spurge have supported growing research investigating natural control mechanisms [19].  Leafy spurge is an invasive weed offering great potential for the use of biological control methods.  A wide spectrum of control organisms exist within its native Eurasian habitat and several is currently being evaluated for use in North America. Several host specific phytophagous insects may provide a source of control [38].  However, leafy spurge possesses a large number of native relatives, so high host specificity is needed for biocontrol organisms.  Thus, research for natural enemies should focus upon two criteria [83]: 1) Does the biological agent possess a broad enough host range to accept the diverse forms and hybrids of leafy spurge? 2) Is the host range narrow enough to exclude the majority of native spurges, especially rare species? A successful biological control project reduces the pest population density to environmentally or economically acceptable levels.  Biological control does not eradicate the target species. Residual populations of the invasive species are required for maintaining populations of the natural enemy [43].  

Fungal control of leafy spurge may offer another control option [107].  Rhizoctonia solani and other multinucleate Rhizoctonia spp. endemic to uncultured soils of Montana and other states of the northern plains show potential as control agents. Rhizoctonia spp. have been observed to produce stem rot at the soil line within infested areas of Montana, Colorado and North Dakota. Studies are currently evaluating host range [16].  The fungus Alternaria tenuissima f. sp. euphorbiae, a natural member of the northern Great Plains ecosystem, weakens leafy spurge [52].

The flea beetles of the genus Aphthona are the most promising approved biological control agents for leafy spurge [90,97,104].  In Montana, beetles in the Aphthona genus have persisted and reduced leafy spurge densities [89]. Aphthona adults emerge from mid- to late June, laying eggs until early September.  Eggs are laid on the soil near leafy spurge crowns.  Adults induce some stress by feeding on foliage.  Control is achieved through stress imposed by larvae feeding upon leafy spurge roots.  After overwintering, larvae pupate in the late spring to early summer [90]. Since eggs are laid on the soil surface, establishment is limited in areas with extensive litter [30].  An effort to refine laboratory techniques providing a method for mass production of Aphthona and other specialist phytophagous insects is currently underway.  Successful rearing of insects in laboratories would replace the need for foreign importation [44]. 

Insects released for leafy spurge control in Montana as of 1992 are as follows [97]:

Scientific name	Type	Part attacked	Date released	Status
Hyles euphorbiae	moth	leaves / flowers	1966	established - 1
Chamaesphecia empiformis	moth	roots	1977	not established
Oberea erythrocephala	beetle	stems / roots	1982	established - 2
Aphthona flava	flea beetle	roots / leaves	1985	established - 2
A. cyparissiae	flea beetle	roots / leaves	1987	established - 2
A. czwalinae	flea beetle	roots / leaves	1987	Established - 2
A. nigriscutis	flea beetle	roots / leaves	1989	Established - 2
Spurgia esula	fly	shoot tips	1985	established - 2

1 - widely established or in large numbers at numerous sites
2 - established in small numbers at few sites

To access further information or to obtain control species, contact the USDA Animal and Plant Health Inspection Service (APHIS), or consult local insectaries [56].  

Chemical control:
The annual application of herbicides provides effective control of leafy spurge. Several studies [1,65,66] document the effectiveness of picloram as a herbicide for long-term control of leafy spurge.  Results vary between regions [7]. Picloram when combined with 2,4-D also provides effective leafy spurge control [62]. The use of picloram does not diminish the viable soil seed bank.  Picloram does not inhibit the germination of leafy spurge seed [14]. Small amounts of picloram are released into the soil from leafy spurge roots when it is applied to foliage.  Exudation occurred 12 hours after application and usually continued at a constant rate for 120 hours.  The percent exuded was not affected by increasing picloram rates [42].

The poorest absorption of picloram occurs during summer dormant periods.  Absorption is maximized during periods of rapid vegetative growth and periods of high humidity such as early morning or late evening.  The effectiveness of picloram depends upon translocation from shoots to roots [67]. However, translocation of herbicide throughout the extensive rooting system is limited [11].  Maximum root translocation occurs during flower development [67].  Imidazalinone herbicides provide effective control of leafy spurge [72,73,82]. Of the imidiazolinone herbicides imazapyr is absorbed more readily than imazethapyr [72]. Imazpyr also provides better long-term control than imazethapyr. The effectiveness imazethapyr tends to decrease 1 year after application [82]. Although imazapyr provides good control of leafy spurge, desirable forage grasses may be severely injured. Imazapyr was found to injure smooth brome (Bromus inermis), creeping bentgrass (Agrostis stolonifera), timothy, little bluestem, big bluestem, and Indian grass (Sorghastrum nutans) [73].

Grazing:
Domestic goats and sheep may help control leafy spurge. Angora goats find leafy spurge palatable [36,93]. They selectively utilize leafy spurge [19], sometimes causing large decreases in stem density. However, favorable results are directly related to the grazing regime employed.  Season-long grazing by goats can reduce leafy spurge densities, while rotational grazing produces little or no effect [59].  In North Dakota changes in grass and leafy spurge production were monitored in conjunction with season-long grazing by Angora goats.  After 3 years of grazing a significant (p < 0.05) reduction in leafy spurge production and a significant (p < 0.05) increase in graminoids were found within a 15.2-acre (6.1-ha) site [93].  Grazing may also prevent leafy spurge from flowering and setting seed [36]. Johnston and Peck [47] observed leafy spurge controlled to a nonspreading stubble after 4 years of domestic sheep grazing.

An article by Anon [2] published in the National Lamb and Wool Grower, provides suggestions for use of domestic sheep: 1) start grazing early spring when spurge is 2 to 6 feet tall, 2) rotate pastures to control seed production, 3) corral sheep for at least 7 days if leafy spurge is grazed after seed set.

Domestic sheep and goats do not aid in leafy spurge expansion if managed properly. In Montana Suffolk sheep and Spanish goats were fed either 3000 or 1500 leafy spurge seeds in either alfalfa pellets or whole barley.  Only 18% of ingested seeds were found in fecal material, with 82% being digested.  Recovery of leafy spurge seeds declined as days after ingestion increased, with goats passing seeds faster than sheep.  Goat fecal matter was seedless after 5 days; sheep after 9 days. A 9-day corralling is recommended after leafy spurge ingestion to allow viable seeds to pass before grazing of non-infested lands [54].  

Commercial grinding may destroy leafy spurge seeds. After they were included in a feed pellet mix, no viable leafy spurge seeds were found in feed pellets that had been ground and processed [18].

A study in Idaho evaluated domestic sheep and goat foraging behavior in relation to forage choices: leafy spurge paired with arrowleaf balsamroot (Balsamorhiza sagittata) or crested wheatgrass.  Grazing habits upon leafy spurge were significantly (p < 0.0001) affected by the animal species and the forage choice alternative to leafy spurge, with leafy spurge having a higher palatability for goats. Percent leafy spurge intake when paired with arrowleaf balsamroot and crested wheatgrass are summarized below [102]:
                            

	leafy spurge & arrowleaf balsamroot	leafy spurge & crested wheatgrass
Sheep	25	32
Goat	33	80

As pastures were progressively defoliated, sheep used more effort than goats selecting an alternative forage to leafy spurge.

Integrated pest management (IPM):
Researchers from North Dakota have found success using Aphthona spp. beetles along with the application of picloram and 2,4-D [80].  Preliminary evidence in North Dakota suggests fall herbicide treatments combined with the presence of flea beetles to accelerate leafy spurge reductions. An integration of picloram plus 2,4-D applications following spring grazing in North Dakota showed better results than grazing alone. Increases in leafy spurge density after spring herbicide application and fall grazing are unexplained as of yet [59].

The use of the foliar fungal pathogen  Alternaria angustiovoidae in conjunction with picloram and 2,4-D may allow for a relative reduction in herbicide rates while maintaining equivalent leafy spurge control [48].  

GENERAL BOTANICAL CHARACTERISTICS :

Leafy spurge is an introduced perennial forb [105]. It generally grows in clumps, producing stems up to 3 feet (0.9 m) tall from caudices, rhizomes, and roots [35]. Stems are tough and woody with variable degrees of branching [94]. The alternate, sessile [11] leaves are broadly narrow with entire margins [35,103]. Leaf length is variable [11], usually 1 to 4 inches (2.5-10 cm) [105]. Leaves subtending the inflorescence are whorled. Flowers are borne in terminal, umbel-shaped cymes [103]. The fruit is a capsule with 3 seeds [5,105]. Seeds are oblong, 0.07 to 0.10 inch (2.0 - 2.5 mm) long and 0.05 to 0.06 inch (1.3 - 1.5 mm) wide, with a caruncle at one end [18,103].

Leafy spurge has an extensive underground rhizome and root system [11]. Roots can penetrate into the soil as far as 15 feet (4.6 m) to 30 feet (9 m) [86]. A large concentration of roots is typically seen at 8 feet (2.4 m) [87].  Underground organs consist of long and short rhizomes, and roots, that extend horizontally in the upper soil and vertically throughout the soil profile.  Deep rooting and thick, corky root bark help establish drought resistance [87,94]. The primary root shows vigorous indeterminate growth [87].  Large amounts of carbohydrates and nitrogen are stored within rhizomes and roots during fall and winter [40].  Reserves accumulate in the fall as top-growth dies.  Reserves are in low supply during the growing season [69].

Latex is present throughout the entire plant [10] at all life stages [94].

RAUNKIAER [88] LIFE FORM:

Hemicryptophyte
Geophyte

REGENERATION PROCESSES:

Leafy spurge reproduces vegetatively and by seed. [11,103,105]

Seed:  Leafy spurge has good seed regeneration, producing large numbers of viable seed [11].  Copious amounts of pollen and nectar [11,103] attract insects for pollination.  Self- and wind pollination is almost non-existent  [94,103]. Flowering shoots normally produce 10 to 50 fruits, with each flowering shoot able to produce and disperse over 200 seeds. The fruit has explosive dehiscence when dry, projecting seed up to 15 feet (4.6 m) [5,11,105]. Capsules erupt and eject seed during periods of high temperature and low humidity [94].

Successful dissemination occurs by water, animals, and self-propulsion [5]. Colonization of previously uninhabited streambeds and riverbanks is associated with the buoyant properties of the seed [11]. Domestic and wild animals including birds and insects, especially ants, act as agents of dispersal [84,94]. Ground-nesting mourning doves may aid in leafy spurge seed dispersal.  No viable seed is found in adult dove fecal matter; however, nestlings pass viable seed [13].

Once seed is disseminated, soil-stored seed may retain viability for 5 to 8 years [5,105]. Germination begins in  April, with most germination occurring in May.  Emergence is maximized within the first 0.5 to 2.4 inches (1.3-6 cm) of soil [87], but germination may occur within the first 4 inches (10 cm) of soil.

Vegetative reproduction:  Leafy spurge is a strong root, rhizome, and root crown sprouter [20]. An extensive rhizome and root system, and the ability to produce adventitious shoot buds on rhizomes and roots, support leafy spurge's vigorous persistence [87]. New shoots arise from numerous pink buds [105] located anywhere along rhizomes and roots [20,94]. The potential for underground buds to produce new shoots is unrelated to bud size or location underground [81].  Large amounts of carbohydrates and nitrogen are stored within rhizomes and roots and are utilized during shoot growth in the spring [69].  Vegetative shoots emerge earlier than leafy spurge seedlings [94]. 

Injury enhances production of vegetative buds on rhizomes and roots [86].  Tillage increases the formation of underground buds and subsequent shoot generation.  After a major portion of the leafy spurge rhizome and root system was removed, vegetative shoots emerged for 5 consecutive years from a depth of 3 feet (0.9 m) in Saskatchewan [94]. Roots at depths of 9.2 feet (2.8 m) have a regeneration capacity similar to those near the soil surface [87].

SITE CHARACTERISTICS:

Leafy spurge achieves greater vegetative reproduction, deeper root penetration, and a greater ability to withstand control treatments in coarse-textured soils than in fine-textured soils.  Soil type has no apparent effect on root biomass but does influence distribution within the soil profile. In coarse-textured soils a higher proportion of roots occurs in soil profiles from surface to 6-inch (0 -15 cm) depths and depths below 30 inches (76 cm) than in similar profiles in fine-textured soils [94].

Leafy spurge prefers disturbed soils. It commonly occupies fields, roadsides, stream valleys, open woodlands, and waste places. A 924-acre (374 ha) contained 83 colonies of leafy spurge, and 95% of the colonies were associated with anthropogenic disturbance.  The number of colonies within each disturbance area was:

49 - trails, fire-guards, and road construction
30 - disturbance caused by track vehicles
4   - no visible soil disturbance

No colonies were associated with natural disturbance from pocket gophers [8].

SUCCESSIONAL STATUS:

Leafy spurge can rapidly invade disturbed sites by establishing from seed and by sprouting from existing roots and root crowns [37,94,106]. Once established, leafy spurge tends to expand and persist. Patches of leafy spurge may expand throughout the growing season under favorable moisture conditions [94]. The mean rate of spread, in feet, for leafy spurge within different habitats was monitored in the Saskatchewan over 2 years.  Results were as follows [94]:

Location and Habitat	Radial increase 1957	Radial increase 1958
Native grassland, grazed	2.50	2.81
Native grassland, grazed	1.27	NA
Native grassland, grazed	0.78	2.31
Abandoned, naturally revegetated, grazed	2.90	-0.47
Cultivated, seeded to bromes in 1956	0.63	3.93
Mixed brome and crested wheatgrass	1.21	1.41
Cultivated (alternate crop and summer fallow)	2.57	NA

 

SEASONAL DEVELOPMENT:

Seedlings can appear as early as May, even when temperatures are freezing.  With adequate soil moisture seed germination may continue throughout the growing season.  Seedling top-growth begins to dry out towards the end of the growing season [78].  With little or no competition from other plant species, seedling shoots may persist until the end of the growing season; however, root growth is usually more vigorous than shoot growth [37].  Within a Saskatchewan mixed-grass prairie, 5% of 7-day-old seedlings severed 1 inch (2.5 cm) below the soil surface regrew [94]. 

The primary root is developed at an early stage of embryo development [86].  Seedlings develop extensive root systems in a relatively short period of time [94]. Spring growth begins with the production of adventitious shoots arising from the seedling root system. Mature leafy spurge fields are an accumulation of adventitious shoots produced from plants a year or more old. New adventitious shoots are from produced early in the growing season until the middle of June [94].  In Saskatchewan the first appearance of vegetative shoots occurred between April 17 and May 1, with vegetative buds appearing on plants as young as 7 days (4-leaf stage) [94]. 

In July a decrease in vegetative shoots corresponds with the increased production of flowering shoots. Flowering occurs throughout the growing season. Flowering shoots appear as early as late April to May, with obvious inflorescences by June.  Fruit matures after 4 to 6 weeks, usually late June or early July [20,37].  Late-season flowering shoots may form in August, with fruit maturing from September to October [37].  During late autumn (during the period of vegetative shoot senescence), root crown buds elongate to just below the soil surface, where they are winter hardened [32]. 

In Minnesota underground development is rapid and early.  Leafy spurge produces stems in late April. Fruit ripens and seeds are dispersed from late June to August [11].

FIRE ECOLOGY OR ADAPTATIONS:

Leafy spurge sprouts from the roots, rhizomes, and root crown after top-kill by fire.

Fire regime: As a non-native species, leafy spurge has no historic fire regime in North America. However, leafy spurge may alter fire intensity within the communities where it occurs. Leafy spurge contains 7 to 9 % oil, which produces nearly as much energy (7758 BTU per pound (4306 kcal/kg)) as wood when combusted  [21]. For information on fire regimes in specific communities where leafy spurge occurs, please read the FEIS summary for the dominant plant species.

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FIRE EFFECTS

SPECIES: Euphorbia esula

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• IMMEDIATE FIRE EFFECT ON PLANT
• DISCUSSION AND QUALIFICATION OF FIRE EFFECT
• PLANT RESPONSE TO FIRE
• DISCUSSION AND QUALIFICATION OF PLANT RESPONSE
• FIRE MANAGEMENT CONSIDERATIONS

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Euphorbia esula: References

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1. Alley, H. P.; Vore, R. E.; Whitson, T. D. 1983. A summary of original and three repetitive herbicide treatments for control of leafy spurge (Euphorbia esula L.) Proceedings, Western Society of Weed Science. 36: 87-93. [35785]

2. Anon. 1990. Noteworthy collections: Arizona: Euphorbia esula L. (Euphorbiaceae). Madrono. 37(1): 60-65. [10615]

3. Baker, H. G. 1986. Patterns of plant invasion in North America. In: Mooney, Harold A.; Drake, James A., eds. Ecology of biological invasions of North America and Hawaii. Ecological Studies 58. New York: Springer-Verlag: 44-57. [17511]

4. Baker, J. L. 1996. Expression of Aphthona nigriscutis from rangeland onto chemically treated pastures. Leafy Spurge News. 18(1): 5. [29942]

5. Bakke, A. L. 1936. Leafy spruge, Euphorbia esula L. Research Bulletin 198. Ames, IA: Iowa State College of Agriculture and Mechanic Arts, Agricultural Experiment Station, Botany and Plant Pathology Section. 246 p. [35770]

6. Beck, K. G.; Sebastian, J. R. 1991. First year results of leafy spurge control with sequential spring and fall herbicide applications. Leafy Spurge News. 13: 13. [16986]

7. Beck, K. George. 1990. Leafy spurge control with glyphosate compounds. In: Leafy spurge symposium: Proceedings and progress reports; 1990 July 10-12; Gillette, WY. [Place of publication unknown]: Great Plains Agricultural Council: 17-20. [13105]

8. Belcher, Joyce W.; Wilson, Scott D. 1989. Leafy spurge and the species composition of a mixed-grass prairie. Journal of Range Management. 42(2): 172-175. [6892]

9. Bernard, Stephen R.; Brown, Kenneth F. 1977. Distribution of mammals, reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's associations for the eleven western states. Tech. Note 301. Denver, CO: U.S. Department of the Interior, Bureau of Land Management. 169 p. [434]

10. Best, K. F.; Bowes, G. G.; Thomas, A. G.; Maw, M. G. 1980. The biology of Canadian weeds. 39. Euphorbia esula L. Canadian Journal of Science. 60: 651-663. [35539]

11. Biesboer, D. D.; Koukkari, W. L. 1992. The taxonomy and biology of leafy spurge (with special reference to the leafy spurge problem in Minnesota) Leafy Spurge News. 14(2): 17-18. [20591]

12. Biesboer, David D.; Koukkari, Willard L. 1990. Control of leafy spurge along rights-of-way with burning and herbicides. In: Leafy spurge symposium: Proceedings and progress reports; 1990 July 10-12; Gillette, WY. [Place of publication unknown]: Great Plains Agricultural Council: 15. [13103]

13. Blockstein, David E.; Maxwell, Bruce D.; Fay, Peter K. 1987. Dispersal of leafy spurge seeds (Euhorbia esula) by mourning doves (Zenaida macroura). Weed Science. 35: 160-162; 1987. [475]

14. Bowes, G. G.; Thomas, A. G. 1978. Longevity of leafy spurge seeds in the soil following various control programs. Journal of Range Management. 31(2): 137-140. [190]

15. Bultsma, Paul. 1990. Weeds, wildlife, and hunters. Wyoming Wildlife. 54(9): 10-15. [14374]

16. Caesar, A. J.; Rees, N. E.; Spencer, N. R.; Quimby, P. C., Jr. 1993. Characterization of Rhizoctonia spp. causing disease of leafy spurge in the Northern Great Plains. Plant Disease. 77: 681-684. [22114]

17. Carlson, R.; Mundal, D.; Nelson, J. 1993. NDSU entomology department leafy spurge work in 1992. Leafy Spurge News. 15(1): 1. [20807]

18. Cash, S. Dennis; Zamora, David L.; Lenssen, Andrew W. 1998. Viability of weed seeds in feed pellet processing. Journal of Range Management. 51(2): 181-185. [28433]

19. Chamrad, A. Dean. 1991. Natural approach to management and control of leafy spurge. Leafy Spurge News. 13(1): 1-2. [18718]

20. Cole, Margaret A. R. 1991. Vegetation management guideline: leafy spurge (Euphorbia esula L.). Natural Areas Journal. 11(3): 171-172. [15251]

21. Davis, Edward S. 1990. The fuel value of leafy spurge pellets. Leafy Spurge News. 12(3): 6-7. [18720]

22. DeLoach, C. Jack. 1991. Past successes and current prospects in biological control of weeds in the United States and Canada. Natural Areas Journal. 11(3): 129-142. [15248]

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