Resource Database


Resource Number: 14528
Title: Major Hardwood Defoliators of the Eastern United States
Description: A variety of leaf-eating insects periodically defoliate hardwood trees in forests, on recreation sites, and in residential areas in the Eastern United States. An occasional defoliation during the life of a forest stand probably has little effect on the overall growth of the stand, but several years of severe or varying levels of defoliation can have negative impacts on the forest community: Increased susceptibility to other insects and diseases, reduced foliage, and altered wildlife habitat. In recreation areas, the unsightliness of defoliated trees can result in decreased visitor use and revenue. A homeowner with a wooded lot plagued with defoliating caterpillars may incur the expense of spraying and possibly the cots of tree removal if mortality occurs. The insects discussed here complete one generation each year. The adult moths lay eggs, and in the spring these eggs hatch into caterpillars, or larvae, the most familiar life stage. It is the larvae that eat the leaves of the trees. After 4 to 6 weeks of feeding, larvae spin cocoons and enter a resting (pupal) stage. In about 2 weeks moths emerge, mate, and begin the life cycle once again. Caterpillars feed on leaves in different ways. A "free feeder" will eat most of the leaf material (fig 1). Some larvae, called leaftiers, construct feeding shelters by tying several leaves together(fig 2). The caterpillar lives and feeds within this mat of leaves, adding more leaves for food as needed or moving to other leaves. Other larvae are leaf rollers, which make a feeding shelter by rolling up the edge of a leaf and live and feed within this roll (fig. 3). Another roll is constructed when the food supply is exhausted or the roll becomes unsuitable for food or shelter. Some common names of these insects are derived from their peculiar method of movement – measuring worms, inchworms, loopers, spanworms, and cankerworms. The movement is produced as the larva brings its hind legs up to the forelegs, forming a loop with the body and then extends the forelegs forward. A behavioral trait shared by the loopers, tiers, and rollers is the reaction of the larvae when they are disturbed. The slightest jarring of the branch or leaf they are on causes larvae to fall or descend on silken threads to other branches or leaves, where feeding continues. To help landowners and others to identify these defoliating pests, this booklet describes eight insects and details their life stages. For positive identifications of these insects and control recommendations, consult your county agricultural agent, State experiment station and the U.S. Department of Agriculture.
Last Updated: January 19, 2021
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