Tansy ragwort

Asked July 15, 2018, 3:23 PM EDT

We have a pasture that has some. Mostly in a corner the horses ignore. We seed and feed in spring and there’s plenty of good grass. When I learned about the plant, I had my husband spray them all and they died but are still there. Do I need to remove them ? It would be a lot of work. Is it dangerous after it’s died ?

Lane County Oregon

1 Response

Tansy ragwort has toxins which accumulate in the body and can cause irreversible liver damage primarily in horses and cattle. Most animals will not consume tansy ragwort if there is plenty of other forage available, but not always. If there are active bio-control, such as cinnabar larvae eating the plants, it may be worth leaving a small patch. Management strategies this time of year would be digging, clipping or mowing to keep the plants from spreading more seed. Herbicides treatments are most effective when the plants are in the rosette stage, sometimes in the fall, definitely in the spring (March-May). Tansy ragwort tends to be more palatable after it is sprayed and does remain toxic in hay.
This link goes to an article I wrote in the spring about tansy ragwort and goes into more detail: https://extension.oregonstate.edu/take-action-right-now-manage-tansy-ragwort