There are two caterpillars in our region, the eastern tent caterpillar and the fall webworm. The placement of the webbing on the tree will help identify which caterpillar is present.
The eastern tent caterpillar is active in the spring and typically spins a web in the crotch of fruit tree branches, such as apple and black cherry trees. The fall webworm becomes active in early summer and spins a web around leaves on the outer branches of trees, and this webbing is seen throughout the growing season. Fall webworms are typically found on pecan, sourwood, persimmon, hickory, sycamore, and fruit trees and are native to the United States. Fall webworms are 1 inch long with a black to reddish head and light yellow to greenish body with 2 long black stripes. They are covered in long, white hairs.
The fall webworm overwinters in mulch or soil as a pupa in a cocoon. The adult fall webworm moth emerges in the spring and begins laying masses of eggs on the underside of leaves. Young caterpillars start by feeding on the surface of the leaves. As the caterpillars mature, entire leaves are consumed. The caterpillars spin webs around the leaves they feed on to protect themselves from predators. The webbing starts out small but grows to include fresh leaves as the caterpillars grow. Their damage is generally only cosmetic to healthy trees.
If management is desired and the webbing is accessible from ground level, it can be removed with a pole. Even just breaking up the webbing makes the caterpillars more vulnerable to their natural enemies, such as birds, stink bugs, and wasps. If an insecticide is chosen, be sure to apply it when the caterpillars are small and more vulnerable. Insecticides containing Bacillis thuringiensus (Bt) or spinosad are safer to apply, effective, and are less toxic to beneficial insects. Insecticides should be applied to the foliage closest to the webbing. As always, follow label directions.
For more information on fall webworms, please visit the Home and Garden Information Center website at hgic.clemson.edu. Tune in on Tuesday nights to watch “Making it Grow” at 7pm on SCETV or mig.org. Email Outen at callenb@clemson.edu.
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