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Fall Webworm  EFW092507 


IMPORTANCE:
Large tent-like webs of the fall webworm (Hyphantria cunea) are a common sight in Alabama. Fall webworms attack persimmon, pecan and occasionally other hardwoods. It is not considered an economic forest pest, but is unsightly and occasionally does considerable damage to pecan groves.

IDENTIFICATION: The adult moth has a wingspread of
1 - 1 1/4 inches and is usually snowy white. The larvae are about
1 1/4 inch long and covered with groups of long silky hairs. Body color varies from pale yellow to gray or brown, with black, orange or yellow spots. Pupae are brown and found inside a gray cocoon constructed of silk, boring dust and other debris. Eggs are small, yellow or light green, turning gray before hatching.
SIGNS OF ATTACK: The first sign of attack is usually a large unsightly silken web on terminal branches around the tree crown, and skeletonized leaves. Examination of the web will reveal large numbers of caterpillars.

LIFE CYCLE: Moths emerge in spring and, after mating, females lay eggs on undersides of leaves of the host. Eggs hatch in about two weeks and larvae immediately begin to feed and construct tent-like webs. They remain inside the web, enlarging it as they feed for four to eight weeks. Fully-grown larvae leave the web when ready to pupate. They spin the pupa cocoon in a sheltered place or in the duff or soil. Adult female moths of the last generation lay eggs in mid-summer. Larvae complete feeding in late fall and overwinter as pupae. There are at least two generations a year in Alabama.

CONTROL: Disease, starvation, predators, parasites, and unfavorable weather take a toll on these insects. If forest control is necessary due to severe and repeated infestation, spray trees with 0.25% malathion. (Mix 3 1/4 pts. of 57% malathion E.C. with 100 gal. of water or fuel oil; or 1 T/gal.) or 0.25% sevin (mix 2 1/2 lbs. of 80% sevin wettable powder with 100 gal. of water, or 2 T/gal.). For shade trees, pick larvae and burn web, or spray as above, eliminating fuel oil as a carrier. Commercial pecan groves have little trouble if a regular spray schedule is followed.

Photo Credits: Keith Douce, The University of Georgia, Lacy L. Hyche, Auburn University, www.forestryimages.org

PDF Version

Fall Webworm Photo 
Fall Webworm 1
Fall Webworm 2 

 Additional Resources:
www.bugwood.org
Eastern Forest Environmental Threat Assessment Center
Forest Encyclopedia, USDA Forest Service Research Station's
Forest Health Protection-USDA Southern Region