Is It Fall Already?

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Fall webworms, one of our native insect pests, are a perennial nuisance and in some cases a destructive pest. They have been showing up at the ends of tree branches all over our area. We’re seeing them in sourwood, choke cherry, other Prunus species, sweet gum, and many others. These “worms” have actually been recorded on hundreds of plant species. The common name is a bit misleading. For one, these are caterpillars, not worms; they’re the larval form of a white moth. Also, these caterpillars can be seen building their webbed tents not just in the fall. As we’ve already seen these caterpillars are active from July through September. Here in NC fall webworms have at least two generations per year.

These tiny, hairy caterpillars hatch and grow into pale to dark caterpillars about 1.5 inches long and are covered with long hairs. Fall Webworms actually feed on over 600 species of trees and shrubs causing mostly cosmetic damage to deciduous trees because of the ugly webs they make around the leaves they’re eating. While they’re not appealing to look at, the danger to the tree that they’ve chosen to feed on isn’t horrible. Since it is already mid-summer the trees have been storing food for a while now, and fall is on the way so the tree would lose the leaves anyway.

Fall Webworms mature in about 6 weeks, leave the web to pupate. They’ll spend the winter in cocoons hidden in crevices of trees or leaf litter, mulch, leaf debris and in the soil. Clearing and cleaning up at the end of the season can help reduce the population of this pest before the white moths can emerge and begin laying eggs from May to August.

Image of a webworm tent

Fall Webworm tent. Photo by M. Daughtry

If you feel that you must take action to deal with the caterpillars, they can be easily destroyed or dislocated by pulling down the webs and destroying them if the webs are within reach of a stick or pole. This also exposes caterpillars to bird and wasp predation. Please remember, just as with the Eastern Tent Caterpillar webs, trying to burn them out of the tree is much more dangerous than it is effective and is not recommended. If the webs are not within reach a power sprayer may be able to reach higher in the tree. If you just must use insecticide to deal with these caterpillars, remember that the web bags will enlarge as the caterpillars grow and need to feed, so apply treatment to cover the foliage closest to the web mass with the pesticide product you choose. Spraying the web itself does not give good contact with the caterpillars. Use pesticides only according to the directions on the label.

Read more about control measures:

2017 Southeastern US Pest Control Guide for Nursery Crops and Landscape Plantings