Biological control of tansy ragwort (Senecio jacobaeae, L.) by the cinnabar moth, Tyria jacobaeae (CL) (Lepidoptera: Arctiidae), in the northern Rocky Mountains.

The control of tansy ragwort on the coast of western North America is a major success story for weed biological control. However, tansy ragwort is still expanding into the colder interior regions of the Pacific Northwest of the United States where previous efforts to establish the same complex of agents have failed. We have successfully established one of the agents, the cinnabar moth, Tyria jacobaeae L., on a major new tansy ragwort infestation in the mountains of northwestern Montana. The cinnabar moth is still expanding its range, but in the areas where first released, it has given excellent control, having eliminated tansy ragwort as a visible component in the forest ecosystem while not impacting native Senecio species. Although establishment in other areas has been slower, we predict that we will eventually control tansy ragwort over most of its range in the northern Rocky Mountains of the United States.