Author
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SEEFELDT, STEVEN |
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Submitted to: Western Society of Weed Science Meeting Proceedings
Publication Type: Abstract Only Publication Acceptance Date: 2/17/2006 Publication Date: 3/15/2006 Citation: Seefeldt, S.S. 2006. Using sheep to reduce exotic weeds in eastern Idaho: their potential as biocontrol agents. Western Society of Weed Science Meeting Proceedings. Interpretive Summary: Exotic weeds are rapidly expanding into the rangelands of Western North America. In Eastern Idaho, downy brome, Russian knapweed, spotted knapweed, and leafy spurge have established dense infestations of relatively discrete patches. Research at the USDA-ARS-United States Sheep Experiment Station and in other locations has demonstrated that strategically timed sheep grazing can be used to reduce the impact of these species on native vegetation. Because different weeds develop and become excellent forage at different times during the growing season, sheep can be moved easily from one weed species to another. It is possible to graze sheep almost exclusively on exotic weeds during the grazing season in Eastern Idaho. This type of grazing could result in season long managed biocontrol of these problem weeds while providing high quality forage for sheep. Altering sheep grazing from traditional patterns to one where exotic weed control is an important component will, not only help land managers improve vegetation management, but will also add value to sheep grazing operations. Technical Abstract: Exotic weeds are rapidly expanding into the rangelands of Western North America. In Eastern Idaho, downy brome, Russian knapweed, spotted knapweed, and leafy spurge have established dense infestations of relatively discrete patches. Research at the USDA-ARS-United States Sheep Experiment Station and in other locations has demonstrated that strategically timed sheep grazing can be used to reduce the impact of these species on native vegetation. Grazing downy brome in the spring before seeds are in the soft dough stage and a second grazing 3 to 4 wks later to reduce regrowth controlled the weed after two consecutive yrs. Sheep grazing on Russian knapweed reduced flower production, especially later in the season. Sheep grazing on spotted knapweed at the bolt to early flower stage reduced seed production and increased native forbs and grasses in Eastern Idaho. Leafy spurge biomass and seed production were reduced and forb cover was increased when sheep grazing was timed to occur when leafy spurge was developing flower bracts. Traditionally in Eastern Idaho, sheep are grazed at lower elevations of the sagebrush steppe in the spring, in the mountains during the summer, and are returned to the lower elevations in autumn. They are moved to a feed lot or to states further south (e.g. Utah or California) at the end of the grazing season. The alternative rotation for sheep grazing would graze sheep at different infestations of weeds at times when they are most vulnerable. This grazing rotation would result in season long managed biocontrol of these problem weeds while providing high quality forage for sheep. |
