NC State Extension Publications

Description and Biology

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Orangestriped oakworms, Anisota senatoria, are sometimes very abundant on oaks in late August and September (they occasionally feed on other hardwoods as well). The moths emerge in June and July and females deposit up to 500 eggs in clusters of several hundred on the underside of oak leaves. The moth is brown with a white spot and a dark stripe on each forewing. Male moths are smaller and have darker but somewhat transparent forewings. The eggs hatch in about a week or so. The tiny, greenish caterpillars eventually grow into splendid, black worms with yellow stripes running lengthwise along their bodies. These caterpillars have a prominent pair of spines or slender horns sticking up behind the head. Young worms feed in groups, whereas older worms tend to be solitary although there may be thousands of caterpillars on a single tree. Small trees are sometimes defoliated completely by mid summer. Even mature oaks are sometimes defoliated to the point of twig dieback due to sun scald or other factors. These caterpillars excrete dark, dry pellets of frass. The larger worms produce many relatively large pellets that rain down from infested trees. As the worms mature, they are often seen crawling along sidewalks and driveways and yards. These caterpillars may wander for a considerable distance while searching for a place to pupate. They dig into the soil three or four inches and pupate there. There is usually one generation per year, and the worms overwinter as pupae in the soil.

Probably orangestriped oakworm eggs and new caterpillars

Young orangestriped oakworms tend to be greenish.

A mature orangestriped oakworm

Older orangestriped oakworms are black with yellow stripes.

Orangestriped oakworms pupa

Orangestriped oakworms pupate underground.

A pair of Orangestriped oakworm moths (the male has darker wings).

Orangestriped oakworm moths have a white spot on each forewing.

Orangestriped oakworm eggs almost ready to hatch and young eggs (insert)

Orangestriped oakworm moths lay their eggs in masses one deep.

Host Plants

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Orangestriped oakworms are most often associated with oaks although they have been collected from other hardwoods including birch, hazelnut, hickory and maple.

Orangestriped oakworms feeding on willow oak in late summer

Orangestriped oakworms are often most damaging to small trees.

A row of oaks some of which have been defoliated completely by orangestriped oakworms

Orangestriped oakworms seem to prefer young landscape trees.

Residential Recommendations

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Control is often complicated by the size of many infested trees. Although small orangestriped oakworms are susceptible to most of the insecticides labeled for home landscape use, most amateur horticulturists do not have sprayers that can reach far up into shade trees where the caterpillars are feeding. By the time the caterpillars descend and crawl about on the soil, they are extremely resistant to pesticides. Fortunately, late summer defoliation is much less damaging to the health of trees than early spring defoliation. In mid to late summer, it is probably better to rely on birds, predators such as paper wasps, diseases, and parasites to lower the population for the next year. In case a tree is small enough to treat, for organic control, use one of the Bacillus thuringiensis or neem extract pesticides but only if the oakworms are young. For mechanical control, knock the caterpillars off the trees and trample them under foot if possible. Shaking limbs with a pole or by rope can cause the caterpillars to drop to the ground. If the tree trunk is small enough, you may be able to thump on the trunk enough to create a rain of caterpillars! (Cover your head!) If orangestriped oakworms are a perennial problem and you are adventuresome, try enhancing the predator population by installing wasp nest boxes nearby next spring.

Other Resources

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For assistance with a specific problem, contact your local N.C. Cooperative Extension center.

This Factsheet has not been peer reviewed.


Professor Emeritus
Entomology & Plant Pathology

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Publication date: Aug. 9, 2023
Revised: Aug. 10, 2023

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