In 1869, the spongy moth, Lymantria dispar, escaped from a Massachusetts lab and became established in North America. It continues to be a serious insect threat to trees and shrubs in the United States.
Spongy moth caterpillars feed on leaves of forest, shade, ornamental, fruit trees and shrubs. Large numbers of them can defoliate a tree by eating 60 to 100 percent of its leaves. Hardwood trees such as oak and hickory may be killed by two or more defoliations, but a single defoliation may kill some evergreens. Some of the spongy moth's favorite host trees are oak, hickory, beech, birch, willow and spruce.
Recognize Spongy Moths and the Signs of Infestation
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What can you do?
You can help detect spongy moth infestations by keeping an eye out for the caterpillars in the spring and searching your property for egg masses later in the year. Female moths will lay their eggs starting in mid-July. Egg masses are tan colored and can be seen on tree trunks and undersides of branches or in sheltered areas, such as under the eaves of houses or in wood piles.
Scrape and Destroy
Scraping egg masses into a container of soapy water or bleach solution is an easy way to kill unwanted spongy moths.
Caterpillar Look-alikes to Spongy Moth
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.