Fall Webworms are making their presence known around the County with several calls coming into the office that past few weeks. Even though you may have seen webs in your trees this past spring, these web makers are different visitors. They are making their homes at the tips of the branches, rather than down between the branch crotches, like the earlier season Easter Tent Caterpillars. Their appearance is completely different as well.
Fall Webworm (Hyphantria cunea) has two generations per season in Ohio. The "fall" in the webworm's common name is based on the appearance of second generation nests late in the season. The first generation began to appear in Scioto County and southern Ohio in late May and second generation caterpillars are now on the scene. Localized fall webworm populations are high throughout the state with nests becoming more evident as they undergo late-season expansion. These tiny, hairy caterpillars hatch and grow into pale to dark caterpillars about 1.5 inches long and are covered with long hairs. Although we see them most often on persimmon, apple and pecan trees, Fall Webworms actually feed on over 600 species of trees and shrubs causing mostly cosmetic damage to shade 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 late summer the trees have been storing food all spring and summer, and fall is on the way so the tree would lose the leaves anyway.
Fall Webworms mature in about 6 weeks, leave the web and pupate on or in the soil. They'll spend the winter in cocoons hidden in mulch, leaf debris and in the soil, so clearing and cleaning up at the end of the season can help reduce the population of this pest before the moth stage can emerge.
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. Insecticide applications should be used sparingly since insecticides may kill bio‑allies that help keep population densities in check. Fall webworms are native to North America and there are over 50 species of parasitoids, and 36 species of predators known to feed on fall webworms. Indeed, it is not unusual to find fall webworm nests surrounded by a compliment of hungry predators including predacious stink bugs. These and other beneficial insects are very effective in reducing year‑to‑year populations of this defoliator. The web also protects the Fall Webworm and spray penetration is almost impossible, therefore spraying the web itself does not give good contact with the caterpillars and will not result in a good kill. Because the web bags will enlarge as the caterpillars grow and need to feed, remember to cover the foliage closest to the web mass with the pesticide product you choose.. Use pesticides only according to the directions on the label. Read more about control measures at https://entomology.ca.uky.edu/ef424