Egg - Oval and about 1 mm long, the egg is grayish-white at first, later acquiring a pinkish hue.
Larva - The first instar larva has a pale yellowish-gray body about 1 mm long with a dark, wide head. The mature larva is also yellowish-gray but has five dark longitudinal stripes with moderately long yellow and light brown hairs and is 13 to 15 mm long. The black head has a well-defined V-shaped mark.
Pupa - The yellowish-brown pupa is 6 to 7.5 mm long, 2 mm wide and occurs within a cocoon about 9 mm long made of silk and soil particles.
Host Plants - Most crucifers and some closely related weedy plants are attacked by cabbage webworms. Hosts include cabbage, turnip, beet, collard, cauliflower, kale, rutabaga, radish, kohlrabi, mustard, rape, horseradish, shepherdspurse, and purslane.
Damage - In North Carolina cabbage webworms do no damage to spring cole crops. In late summer or early fall, however, young plants of the fall crop are subject to attack. By boring into buds, stems, and stalks, webworms destroy or disfigure buds and sometimes kill entire plants. Plants with destroyed buds will produce secondary buds but these are not likely to mature into marketable heads by harvest.
Webworms feeding on the outer leaves of older plants are harmless. Webworms are enclosed by protective silken webs, often hiding along leaf veins on the underside of leaves. They feed during the day, but are fairly inactive during cold weather.
Life History - Little information is available concerning the life history of the cabbage webworm in the southern U.S. Closely related species overwinter as larva or pupae in silk-lined cells in soil. Cabbage webworm moths deposit approximately 300 to 350 eggs on host plant buds. About 3 days later, larvae emerge and feed in the buds, eventually moving to the outer leaves where they spin webs and continue to feed along large leaf veins. They pupate among shed leaves or other refuse on the ground. The number of annual generations in North Carolina has not been determined.
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