caterpillar
moth
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| Web on pecan tree | Fall webworm, caterpillar |
Fall webworm, moth |
Fall webworm caterpillars build large silken webs in pecan trees. One hundred or more caterpillars may be found inside the web, where they feed on pecan leaves. Large infestations may cover the tree with webs and cause severe defoliation.
Biology: Mature larvae are about 1 inch long, pale yellow or green, and covered with tufts of long, white hairs. The adult is a white moth with dark spots on the wings. Female moths emerge in the spring and deposit eggs in masses of several hundred on the undersides of pecan and other tree leaves. The eggs are greenish-white and covered by grey hairs left by the female. There are two to four generations each year, depending upon locality in the state. The last or fall generation is usually the most damaging (see Extension publication L-1811 "Fall Webworms").
Control: Many insect parasites and predators feed on fall webworm larvae and reduce their numbers. Also, insecticides applied for other pecan pests help reduce webworm densities. If webs are common and the potential defoliation appears unacceptable, spot spraying of infested trees may be practical. The insecticide spray must penetrate the web to be effective.