Northern Prairie Wildlife Research Center
|Ranchers need to be patient in awaiting the benefits from
introduced leafy spurge enemies. Some beneficial insects already are at
work on the range, but no dramatic results have been observed because
biological control is a gradual process. Ranchers can help the process
by restricting their use of herbicides and insecticides at and near release
sites so that the insects can multiply without harm from agricultural
chemicals. Still, it takes several years to build up adequate numbers
of a weed's natural enemies at any specific location. When the insects
increase in number and spurge becomes less abundant, the natural enemies
search for other stands of the weed to attack. They continue the process
for as long as spurge is present.
While awaiting the arrival of the insects, ranchers also can help by being careful not to spread spurge into new areas. Spurge has been spread over and over by people who were not aware that they were doing any harm. The seed travels along unobtrusively in hay and as a contaminant of forage seed and grain. Hay contaminated with spurge should not be moved. Cultivating equipment and trucks should be checked before being moved to make sure that the weed has been cleared away.
Ranchers also can make interim use of less exotic "natural enemies." Sheep and goats grazing on spurge-infested land feed on the weed's flowers, thereby reducing seed production. Sheep can safely satisfy half of their diet or more from spurge despite the noxious chemicals in the weed. Even ranchers who traditionally have run only cattle should consider stocking sheep if they have an extensive spurge infestation.