Sunday, August 30, 2009

Landscape - Orangestriped oakworms

The following is information on Orangestriped Oakworms from North Carolina State University. This is an occasional pest in Delaware.

Orangestriped oakworms are sometimes very abundant on oaks in summer. They occasionally feed on other hardwoods as well. The moth is brown in color with a white spot and a dark stripe on each forewing. The moths emerge in June and July and deposit their eggs in clusters of several hundred on the underside of oak leaves. The eggs hatch in about a week. The tiny, green caterpillars eventually grow into attractive black caterpillars with yellow or orange stripes running lengthwise along their bodies. Young caterpillars feed in groups whereas older caterpillars tend to be solitary, although there may be thousands of caterpillars on a single tree. Small trees are sometimes defoliated completely by midsummer.

As the caterpillars mature, they are often seen crawling along sidewalks, driveways and yards. These caterpillars may wander for a considerable distance while searching for a place to pupate. You can step on these without fear, as long as you have on shoes. They dig into the soil three or four inches and pupate there. There is usually one generation per year, and the caterpillars overwinter as pupae in the soil. Control is complicated by the size of many of the infested trees. Most people do not have sprayers that can reach very high into shade trees, and by the time the caterpillars descend and crawl about on the soil they are extremely resistant to pesticides. Fortunately, late summer defoliations are much less damaging to the health of trees than early spring defoliations. In most cases it is probably better to rely on birds, diseases and parasites to lower the population next year.

For more information, see If you would like to consider boosting the paper wasp predator population with nest boxes in the spring, see

Orangedstriped oakworm. Photo by David Cappaert, Michigan State University,

Information from Steve Bambara, Extension Entomologist in the August 28, 2009 edition of North Carolina Pest News

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