The Thistle Seed Head Weevil, Rhinocyllus conicus, is very effective in reducing seed production in this biennial weed. Adult weevils lay an average of 190
Sud Morishita, former Bonneville County, Idaho weed supervisor, estimates that bio-control has reduced the county's use of chemicals to fight musk thistle by as much as 60 percent.
The Thistle Defoliating Beetle, Cassida rubiginosa, feeds on the foliage of musk, Canada, and plumeless thistles. Adults emerge in spring with each female laying an average of 800 eggs. Both the developing larvae and adults defoliate leaf tissue throughout spring, summer and well into the fall in most areas. The degree of defoliation due to this insect is often striking. Releases of 105 adults are available in June and July for $90.00.
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Biological Control of Weeds, Inc.
1418 Maple Drive Bozeman, MT 59715
Phone 406-586-5111 FAX: 406-586-1679