Cinnabar moth

Cinnabar moths, Tyria jacobaeae, were released in Oregon to control the noxious exotic weed, tansy ragwort, Senecio jacobaea. Tansy ragwort showed up in the Portland area in 1922 and spread throughout the state. Livestock and deer that graze on tansy ragwort may suffer fatal liver failure. The economic losses due to livestock feeding on tansy ragwort can be quite high, in the millions of dollars.

In 1976, the Oregon Department of Agriculture declared tansy ragwort a noxious weed. In the meantime, researchers, led by OSU's Peter McEvoy, were searching the original home of tansy ragwort, Europe, for biological control agents. Cinnabar moth was one of three natural enemies released to control the weed. It was first released in the 60's with additional releases thereafter. The grayish-black moths with red patches on the wings established and provide biological control of this weed. The moths lay their eggs on the underside of the leaves of tansy during the late spring. Soon small orange and black caterpillars hatch from the eggs. They feed first on the lower side of the leaves on which the eggs were laid, then move onto the developing flower buds and leaves. They pupate on the ground in the leaf litter. There is one generation a year.

While largely considered a biological control success story, the cinnabar moth larvae can feed on a native plant in Oregon, arrowleaf groundsel, as well as the weed species of groundsel. I've also seen it feeding on a heather (but I don't know if it will survive on that host to maturity). And the cyclic fluctuations in the growth of tansy ragwort may require patience while cinnabar moth populations increase to meet the need.

Additional Reading

Isaacson, D.L. 1973. A Life Table for the Cinnabar Moth. Entomophaga 18 (3) pp. 291-303.

Novak, Teresa. 2005. Researchers are using new bugs, biology and trickiness to fight an invading green army. Oregon Ag Progress. Accessed 25 June 2014.