Submitted to: Journal of Arid Environments
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/12/2006
Publication Date: 1/10/2007
Citation: Seefeldt, S.S., Taylor, J.B., Van Vleet, S.A. 2007. Reducing leafy spurge (euphorbia esula) with a combination of sheep grazing and imazapic. Journal of Arid Environments. 69:432-440. Interpretive Summary: Leafy spurge (Euphorbia esula), a perennial plant of Europe and Asia, invaded the North America Great Plains and Rocky Mountains after its introduction in the early 1880’s. Range management strategies are needed to reduce the spread of this exotic and invasive weed into native rangelands. Our objective for this study was to determine whether early-summer sheep grazing combined with an autumn application of imazapic enhances control of leafy spurge, compared with grazing or imazapic application alone. The results of the study indicate that combining early-summer sheep grazing and autumn imazapic application does not enhance the control of leafy spurge, compared with imazapic application alone. However, carefully timed sheep grazing prevented leafy spurge plants from producing seeds and sustained plant productivity in the pasture. Based on these results, we conclude that sheep grazing can be an important component of leafy spurge control strategies.
Technical Abstract: Two experiments were conducted from 2001 to 2004 to determine whether early-summer sheep grazing combined with an autumn application of imazapic would enhance control of leafy spurge. For Experiments1 and 2, treatments were arranged in a factorial array and were: 1) neither grazing nor imazapic application, 2) early-summer sheep grazing only, 3) autumn imazapic application only, and 4) sheep grazing combined with imazapic application. In Experiment 1, sheep grazing was applied twice (two consecutive summers) before imazapic treatment. In Experiment 2, sheep grazing was applied once before imazapic treatment. Sheep grazing was implemented to remove reproductive parts from leafy spurge within a 10-d grazing period. Imazapic was applied at 210 g ae/ha with 1.25% (v/v) methylated seed oil. In Experiment 1, 1 year of sheep grazing did not alter measured vegetation components, but it did increase the number of grass seeds in the soil. Two years of sheep grazing increased the forb and grass cover component, increased the number of grass seeds in the soil, and kept the leafy spurge seed bank from increasing. In Experiments 1 and 2, application of imazapic reduced leafy spurge stem densities and leafy spurge cover and increased forb cover. The combination of sheep grazing and imazapic did not enhance the control of leafy spurge. However, sheep grazing prevented an increase in the leafy spurge seed bank and sustained plant biomass productivity in the pasture.