• IMPORTANCE TO LIVESTOCK AND WILDLIFE
• PALATABILITY
• NUTRITIONAL VALUE
• COVER VALUE
• VALUE FOR REHABILITATION OF DISTURBED SITES
• OTHER USES AND VALUES
• MANAGEMENT CONSIDERATIONS

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]:

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:

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]:

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].

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].  

Related categories for SPECIES: Euphorbia esula | Leafy Spurge