Caterpillar stage is yellow or green to almost black with a black stripe and numerous black spots on back and up to 1 and 1/4 inches long. The adult is a moth with wavy lines on its wings.
Beet, peas, potato and spinach.
Eats leaves and buds of young plants. Rolls and folds leaves; ties them together with webs.
Throughout United States; especially troublesome in western states.
Destroy weeds in and surrounding garden, especially pigweed and lambsquarters, which may serve as alternate hosts for beet webworms. Clip off webbed leaves and destroy the caterpillars within them.
Pyrethrum spray or dust can be used but must be applied when caterpillars are young, before substantial webbing has been produced. The beet webworm's habit of enclosing itself in folded leaves protects it not only from insecticides but many natural enemies as well. Bacillus thuringiensis (2.0-3.0 tbsp in 1 gallon of water) can also be used.
Treat with a registered insecticide when insects appear in damaging numbers; repeat as needed.
Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Interim Administrator, 1890 Extension Program, Virginia State University, Petersburg.
April 25, 2011