Fall webworm is seen on a tree branch in Oshlkosh on Sept. 9, 2024. / Photo Credit: Bill McNee, Wisconsin DNR

By Bill McNee, DNR Forest Health specialist, Oshkosh;
Bill.McNee@wisconsin.gov or 920-360-0942

The native insect known as fall webworm (Hyphantria cunea) is back in the news.

The caterpillars don’t draw much attention on their own; instead, what catches the eye at this time of year are the large webs (or “tents”) that they create on the tips of tree branches.

These insects make their nests in late summer and early fall, when trees often have already started to shut down for the season, so any impact on tree health is likely to be minimal. Because of that, there is generally no need to take action to remove the nests and caterpillars. Wind and rain will usually break up the webs within a few months.

Fall webworms feed inside a tent. Thanks mostly to the timing of their feeding cycle (in the fall), the insect is generally not a threat to tree health. / Photo Credit: Wisconsin DNR

It should be noted that these caterpillars are a different species than other insects known as eastern tent caterpillar, forest tent caterpillar or spongy moth. Those caterpillars emerge in spring, and each can cause substantial damage to trees.

Fall webworm was the topic of a recent news item produced by WQOW Television in Eau Claire.