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GREATjM RIVERlRIPW GREENING Chemical Foliar treat Canada thistle with clopyralid, glyphosate, or triclopyr. Glyphosate can be used for careful spot treatment or when broadcast treating in areas where there is no cover of desirable species. Clopyralid, a broadleaf herbicide for use particularly on members of the Aster and Legume family, is useful for control of Canada thistle where cover of native species is high. Herbicide should be applied during the rosette stage for best results, but can be applied up until flower buds are formed and again in the fall. Repeat treatments are required. Herbicide can also be applied to cut stems for treatment of small areas. It is essential to apply herbicide to each stem that may be connected by rhizomes. Any missed stems will allow the clone to survive. Continued follow-up treatments will be needed. Biological There are biological control agents available for thistle control. However, caution is warranted as the available weevils have been observed feeding on native thistles. Long-term Management Prescribed fire can have mixed results for Canada thistle control and is best used as part of an integrated management program. Using prescribed fire to increase the health and diversity of fire dependent native plant communities is a recommended tactic. Canada Thistle April May June July Aug Sept Oct Nov Dec - Mar Burn Foliar Herbicide Cut Stem Herbicide Mow Don't mow Flowering Bull Thistle (Cirsium vulgare) Description Bull thistle is a biennial herbaceous plant which develops a rosette in the first year and then sends up a 3-6 foot flowering stalk the second season. The plant is prickly, with spine -tipped lobes on the leaves and stems with prominent ridges armed with spines. The upper surface of the leaves is rough to the touch. Bull thistle is in the composite or Aster Family, so the purple florets are arranged in dense flower - heads. Seeds with their attached plumes are dispersed by wind and may persist in the seed bank for 10 years or more. Bull thistle readily invades disturbed prairies, as well as low quality pastures, fallow fields, and roadsides. It is readily identifiable in over -stocked pastures where the livestock have grazed around it. It is not a significant problem in high quality natural areas where it cannot easily get a foothold. Mechanical Bull thistles can be cut or mowed prior to their going to seed. If seeds have developed, the plant material should be removed from the site. Severing the tap root as deep as possible with a shovel or parsnip predator can kill the plant. This method can be used for rosettes or flowering plants.