Author
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Van Vleet, Stephen |
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Seefeldt, Steven |
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Submitted to: Western Society of Weed Science Meeting Proceedings
Publication Type: Proceedings Publication Acceptance Date: 1/5/2005 Publication Date: 2/5/2005 Citation: Van Vleet, S.M., Seefeldt, S.S. 2005. The control of leafy spurge (Euphorbia esul L.)using strategic sheep grazing and imazapic. In: Proceedings of the Western Society of Weed Science. 58th Annual Western Society of Weed Science Meeting. March 8-10, 2005, Vancouver, Canada. CDROM. Interpretive Summary: Leafy spurge is an aggressive weed competing with native vegetation in rangeland communities. An experiment was conducted to reduce the leafy spurge soil seedbank through sheep grazing and imazapic applications. The experimental design was a randomized complete block with 2 x 2 factorial of grazing and autumn applied imazapic. The four treatments were replicated four times for a total of sixteen pastures. Sheep grazing began each year when leafy spurge flowered, but before mature seed had developed. Grazing continued until reproductive structures were eliminated. Pastures containing sheep as a treatment were grazed for two seasons. Imazapic was applied in the autumn of 2003. Stem counts of leafy spurge were evaluated along with percent cover of grass, leafy spurge and forbs. Imazapic applications decreased leafy spurge stem counts (44 to 1 per 0.18 square meter) and ground cover (62 to 4%) compared to the control. Grass seed banks increased (p<0.05) in the ungrazed treatment (35 to 58) and remained constant in the grazed treatment (23 to 30), however, forb seed banks increased similarly in the grazed and ungrazed treatments (18 to 31 and 14 to 27). Leafy spurge seed banks increased (p<0.05) in the ungrazed treatments (7 to 24) while remaining constant in the grazed treatment (7 to 6). Sheep were effective in preventing an increase in leafy spurge soil seed bank. Technical Abstract: Leafy spurge is a prolific seed producer and can spread rapidly by seed. The objective of this study was to determine the effect of sheep grazing, with or without autumn applied imazapic, on leafy spurge productivity and soil seed banks. The study was conducted on a U.S. Sheep Station cooperative research site (Spencer, ID) from 2002 to 2004. The experimental design was a randomized complete block with 2 x 2 factorial of grazing and autumn applied imazapic. The four treatments were replicated four times for a total of sixteen pastures. Sheep grazing began each year when leafy spurge flowered, but before mature seed had developed. Grazing continued until reproductive structures were eliminated. Pastures containing sheep as a treatment were grazed for two seasons (2002 and 2003). Imazapic was applied the autumn of 2003. Leafy spurge stem counts were evaluated along with percent cover of grass, leafy spurge and forbs. Soil samples were collected from all pastures in late autumn 2002 and 2003. Soil samples within a pasture were combined and seeds in a 1-kg sample were germinated in a growth chamber for determining soil seed bank. Germinated seedlings of leafy spurge, grass and forbs were counted and removed from growth chamber weekly until emergence ceased (6 weeks). No interactions among treatments were found. Imazapic applications decreased (p<0.05) leafy spurge stem counts (44 to 1 per 0.18 square meter) and ground cover (62 to 4%) compared to the control. Grass cover (21 to 53%) was higher (p<0.05) in the imazapic treatment, while forb cover was higher (14 to 68%) in the sheep grazed, autumn-applied imazapic treatment. Grass seed banks increased (p<0.05) in the ungrazed treatment (35 to 58) and remained constant in the grazed treatment (23 to 30), however, forb seed banks increased similarly in the grazed and ungrazed treatments (18 to 31 and 14 to 27). Leafy spurge seed banks increased (p<0.05) in the ungrazed treatments (7 to 24) while remaining constant in the grazed treatment (7 to 6). Sheep were effective in preventing an increase in leafy spurge soil seed bank. |
