|Tansy Ragwort (Senecio jacobaea)|
Tansy ragwort is a weedy, biennial plant that infests woodlands, pastures, and hayfields of the coastal northwest United States. It is generally unpalatable to livestock and, therefore, is eaten only when other food is scarce or when it cannot be avoided as in hay, ensilage, and lush pastures. It is toxic to all classes of livestock but most toxic to cattle and horses. At doses likely to be ingested, it causes a chronic liver disease that is seen as a cirrhosis-like hepatic degeneration. Affected animals generally die within several weeks or months after the tansy ragwort has been eaten. As this is often after the contaminated hay or feed is not available for inspection, it is difficult to definitively diagnose tansy intoxication and death may be attributed to other causes.
Where and When It Grows
Mature tansy ragwort may grow 1.0-1.5 meters tall. It is sturdy stemmed, has a strong "weedy" odor, and produces great numbers of seed. The first year's growth, the rosette stage, is most toxic. Livestock grazing contaminated pastures often cannot avoid eating it as they graze good forage. Tansy ragwort often invades pastures and hayfields and may be found in any open uncultivated place. Rosette, flower, and seed stage plants may be found in the same pasture.How It Affects Livestock
Tansy ragwort contains pyrrolizidine alkaloids, which affect primarily the liver. Cells of the liver are slowly killed and prevented from regenerating to replace damaged tissues resulting in gradual scarring and replacement with connective tissue. Whether an animal survives depends upon the amount and rate of damage. Some animals survive for 6 months or longer after they have ingested a lethal amount of plant. During this latent period they may show no outward symptoms or signs. Later, often without additional exposure to tansy, they may become lethargic, fill with fluid in the abdominal cavity, and die within 2 to 4 days. Such animal may develop central nervous system disease seen as impaired vision and incessant stumbling. The onset of symptoms may be precipitated by other stresses such as pregnancy, lactation or poor nutrition. Often the animal's death is mistakenly attributed to other causes. Animals eating 5 percent or more of their total daily diet of prebloom tansy ragwort for periods exceeding 20 consecutive days can be expected to die within a 6-month period.
Signs and Lesions of Poisoning
may vary, depending on the amount of plant eaten and the rate at which it was
may occur within a few days after symptoms appear
How to Reduce Losses
Research results show that tansy ragwort can be controlled with 2,4-D (low volatile ester or emulsifiable acid) at 0.5-1.0 kg pounds active ingredient per acre, or by dicamba at 0.23 to 0.5 kg active ingredient per acre. Tansy ragwort should be sprayed in the rosette stage. Both herbicides will injure or kill legumes. Follow all precautions for handling herbicides.