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United States Department of Agriculture

Agricultural Research Service

Title: Control of Leafy Spurge by Sheep Grazing.

Authors
item Ries, Ronald
item Karn, James

Submitted to: 2000 Billings Land Reclamation Symposium
Publication Type: Proceedings
Publication Acceptance Date: January 14, 2000
Publication Date: N/A

Interpretive Summary: Leafy spurge is a serious invasive plant on native rangelands and some reclaimed mined land across the Northern Great Plains and northwestern United States. This plant has been difficult to control with herbicides because of expense and collateral damage to other plants and water supplies. Sheep will graze leafy spurge and sheep grazing has been used with varying degrees of success to control leafy spurge. We studied leafy spurge growth and utilization by sheep on 4 range sites (overflow, silty, shallow, and woody draw) within a 891 ha pasture in the Heart River breaks in central North Dakota. We found that leafy spurge grew and produced differently in 1997, 1998, and 1999 and believe that weather conditions during the 3 years are largely responsible for these differences. After grazing this leafy spurge infested pasture with Rambouillet sheep in 1998, we found leafy spurge densities were the same on ungrazed and grazed rangeland. However, leafy spurge dry matter remaining after one season of sheep grazing was significantly less on grazed than ungrazed areas, but leafy spurge utilization was not uniform for all range sites. Sheep preferred grazing the shallow, silty, and woody draw range sites because they were higher in elevation, less confining, with cooler temperatures and fewer insects. Sheep grazing is an important biological control for leafy spurge while providing marketable products for the land owner. Understanding sheep behavior is important when managing a flock for optimum leafy spurge control.

Technical Abstract: Leafy spurge is a serious invasive plant problem on native rangelands and some reclaimed mined land across the Northern Great Plains and northwestern United States. Sheep will graze leafy spurge and sheep grazing has been used with varying degrees of success to control leafy spurge. We studied the use of sheep as a biological control measure for leafy spurge infested rangeland on the Heart River in central North Dakota. Prior to sheep grazing, 10 locations within 4 range sites (overflow, silty, shallow, and woody draw) were identified and caged. Leafy spurge stem density and leafy spurge and other forage dry matter production was monitored for 3 growing seasons prior to sheep grazing. After 1 year of grazing with Rambouillet sheep, the stem density and dry matter production of leafy spurge was measured inside and outside the cages. Data were analyzed by unequal subplot, mixed model analysis of variance. We found that leafy spurge density and production responded to a significant range site x year interaction. After 1 grazing season, leafy spurge densities were the same on ungrazed and grazed rangeland. Leafy spurge dry matter remaining after one season of sheep grazing was significantly less than on grazed than ungrazed areas but the effect was not uniform for all range sites. Range sites (silty, shallow, and woody draw) that were at higher elevations, with significant air movement, were more intensively grazed by the sheep than the overflow range site along a stream bank and in protected areas. Sheep grazing can be an important leafy spurge control option on infested rangelands or reclaimed native grasslands while providing marketable products for the land owner.

Last Modified: 9/10/2014
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