This time of year I get alot of calls about fall webworm from concerned homeowners around Colquitt County. The fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Erebidae) is a polyphagous caterpillar pest of ornamentals and trees in Georgia. “Polyphagous” means that it can feed on many types of food, and the fall webworm is known to feed on more than 600 species of plants, including row crops, herbaceous plants, shrubs, fruit, and ornamental trees in orchards, nurseries, and landscapes. Fall webworm larvae construct silk web nesting to facilitate feeding, to escape the attack of natural enemies, and for heat retention. The webbing is considered unsightly, and feeding on foliage inside the nest leads to extensive defoliation. The fall webworm can quickly reduce the aesthetic appeal of landscape trees and shrubs, and severe infestation can cause considerable damage to trees. Below is an example of fall webworms in Colquitt County…
What is there life cycle? The fall webworm are active during the last summer and early fall. The female can lay over 600 eggs on the underside of leaves and they hatch within a week. The larvae has red or black heads and are covered with fine hair. They form a silken web and they begin to feed. Larvae can feed for up to 6 weeks and then they pupate which can last up to 80 days. This could depend on environment. This pest overwinters as pupa and have multiple generations a year.
What can I do about them? Pruning is a great way to manage this pest. However, intensive pruning is not recommended if populations get out of hand. Beneficial insects such as spiders, insect predators and parasitoids can impact web worm populations. Homeowners can try to control populations by tearing down the protective webs with a long pole. If the nest is disrupted then younger worms will be more vulnerable to beneficial insects.
What can I spray? Insecticides can be used when caterpillars are young but when the nest increases in size then insecticide are less effective. Bacillus thuringiensis (Bt) (Trade names include Biotrol WP, Thuricide, Sok-Btor), and spinosad (Monterey Garden Spray, Bonaid Spinosad Concentrate), can be used for fall webworm control. Many synthetic insecticides are available but spraying larger trees can be an issue due to coverage. The UGA Homeowner Pest Management Handbook can be used for more information.
If you would like more information on fall web worms please go to the publication Fall webworm: Biology and management. or contact your local county Extension agent.
