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TANSY RAGWORT
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Tansy ragwort is a biennial, but can also develop as a short-lived perennial. Seeds germinate in the fall or spring. Tansy ragwort has conspicuous, daisy-like gold flowers, which appear over an extended period. The rosette has irregular, lobed leaves, 5 to 9 inches long, attached directly to the main stalk. Plant color varies from light to dark green. Plants that emerge late in the fall or in the spring are more likely to remain vegetative during the summer and bloom during the second year of growth. If the plant is cut or broken before bloom, it may regrow and flower during the third year. Livestock normally will not graze tansy ragwort if more desirable forage is available. Tansy ragwort contains at least six pyrrolizidine alkaloids. Concentration of alkaloids is greatest in the flowers. This can cause the liver to cease normal function and the animal will die. The liver damage is cumulative with time and dose. Cattle and horses are affected seriously; goats may suffer poisoning; sheep are generally not affected.

Control

Mechnical: Mowing is not effective in reducing tansy ragwort populations. Theoretically, mowing should keep plants from blooming if properly timed. Hand pulling and digging can be effective in keeping second-year plants from setting seed. If plants start to bloom, some viable seed can be produced. Hand labor requires persistence and intensive effort and is most applicable in small isolated areas. Unless the entire root system is removed, regrowth will occur from segments left in the soil.
Biological: Biological control agents provide fair to excellent control, but have not been tested in Idaho. Sheep and goats and have been used as a control agent.
Chemical: Herbicides that have been used with some success are dicamba, metsulfuron, triclopyr, or picloram. Picloram is a "Restricted Use" herbicide and must be applied by a licensed applicator. These products are effective on rangeland, pastures, and other non-crop areas.
When choosing any kind of control method, assure that your choice is suited for your particular situation. Always read and follow the product label before applying any herbicide