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15. Leafy Spurge Control with Sheep.  Marcel Archambault, Agricultural Representative, Manitoba Agriculture.

Leafy spurge, a perennial weed, continues to invade hundreds of thousands of acres across Manitoba. Previous attempts to control spurge using cultivation or herbicides have been largely unsuccessful. In 1993, the Brandon Soil Management Association initiated a project to determine the impact sheep grazing would have on the density and longevity of established spurge infestations. Results to date are very encouraging. Spurge density is recorded each spring to measure the degree of control obtained from the previous grazing seasons. Observations in the spring of 1995 showed the following reductions in spurge density after only two years: paddocks sprayed with 2,4-D only, 44%; paddocks grazed by sheep only, 54%; paddocks sprayed with 2,4-D and grazed by sheep, 61%. Observations of pasture conditions during the 1995 grazing season suggest further control can be expected next spring. Sheep performance has been good in all three grazing seasons. Dry ewes gained an average of 0.167 lb/day in the 1993 and 1994 grazing seasons. In 1995, sheep gains improved to 0.275 lb/day in the sheep only paddocks and to 0.295 lb/day in the sheep plus 2,4-D treated paddocks. In conjunction with this trial, three additional projects are being run. In 1994, a stocking rate trial was initiated to determine how spurge control is related to sheep stocking rates. And in 1995, the Manitoba Sheep Association ran two trials to determine if the undesirable compounds found in spurge could be found in the sheep's blood and to find out if grazing spurge causes off-flavours in meat of animals grazing spurge.

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