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The spongy moth is just one of many insects that feed on tree leaves. There are several caterpillars common to Fairfax County which are often mistaken for spongy moth. Each of these has definite identifying characteristics which are true to the species. No two insect species have the same characteristics. The information provided here will aid you in differentiating the spongy moth caterpillar from others.
Eastern Tent Caterpillar
Caterpillars rest inside the tents during the heat of the day or rainy weather and depart to feed on leaves during the night. While tent caterpillars can nearly defoliate a tree when numerous, the tree will usually recover and put out new leaves.
Eastern tent caterpillar is not as serious a pest as spongy moth because it is a well-established native with many predators and parasitoids that control them. It feeds exclusively on fruit trees like apple, wild cherry, crabapple and plum in May and June.
Caterpillars are quite variable in color; either light green with yellow stripes to green with dark stripes or black with white stripes. They are smooth and hairless. Mature larvae will reach a length of about 1 inch. These "loopers" or "inchworms" hatch in late March or early April. Caterpillars hang by silken threads throughout the caterpillar stage, whereas the spongy moth does so only in the early caterpillar stage.
Caterpillars are pale yellow, green, or brown with two rows of black spots down their backs. They are mainly hairless when young. Pale yellow or light brown hairs appear as they grow. They are 1 1/2-2 inches in length and covered in silky hairs when mature. Caterpillars emerge in late May and feed on a wide variety of hardwood tree species. They build webs at the tips of branches and feed inside them. The webs become noticeable by August, and although these may be considered unattractive, the late season feeding rarely causes lasting damage because the trees have already had plenty of time to store enough energy for the winter. This is a well-established native with many predators, parasitoids, and diseases to control them.
Forest Tent Caterpillar
Caterpillars have pale bluish lines along the sides of a blackish body with a row of cream-colored keyhole-shaped spots down the middle of their backs. They are sparsely covered with white hair and reach two inches in length when mature. They feed in oaks and other broad-leaf trees in late March to early April. They do not make a tent or hang by silken threads, but leave silken threads along branches, often congregating in social masses while molting. This well-established native has many predators, parasitoids, and diseases to control it.
Photo By: William M. Ciesla, Forest Health Management International, Bugwood.org
Orangestriped Oakworm
Caterpillar is black and hairless with eight narrow yellow-orange stripes on its back. At maturity it is about two inches long and has a pair of long, curved ‘horns’ that point forward from its head. It is a common native of eastern North America that prefers oak leaves, especially red oaks. Defoliation becomes noticeable in August and September. Because it is a late-season defoliator with a host of well-established predators, parasitoids, and diseases to control it, it does not pose a serious threat to trees in Fairfax County.
There are many insects that feed on trees. The correct identification of a problem insect is essential to controlling that specific insect properly. Fortunately, the control of most insects is rarely necessary since they seldom cause significant damage.
For more information, please contact the Fairfax County Forest Pest Branch at 703-324-1770, TTY 711, or by email. You may also visit the Virginia Cooperative Extension for more information about pesticide safety and insect identification and control measures.
Spongy Moth
Spongy Moth continues to be a serious insect threat to trees and shrubs in the United States.
