fall webworm (Hyphantria cunea)

Have you seen webs in the trees this summer?

Do you know what causes it? The offending insect that creates the webbed nests is the larval stage of a moth. After spending a cold winter in the duff, and tired of watching TV in its cocoon (some have wifi), the pupae will emerge as an adult as early as late June to deposit eggs on the underside of leaves. These eggs will hatch within a week, quickly becoming a big family of hungry larvae, anxious to start spinning their silken webs over the leaves upon which to feed (most hardwoods are on the menu).
The name of this moth is fall webworm (Hyphantria cunea) and its webs appear in summer! It looks suspiciously like tent caterpillar – but don’t be fooled. Tent caterpillars are a spring insect, hatched and waiting to feed as the host trees leaves emerge.
What to do? Because fall webworm is a “late season insect” and the trees have had much of the spring/summer to produce food (photosynthate) they really cause little harm. Unlike the tent caterpillar, feeding on the emerging leaves of a hungry tree just awakened from a long winters sleep – fall webworm is an aesthetic nuisance – that’s all.
Do nothing? Doing nothing is an option – fall frost will end feeding, starting the cycle over again and the fall rains and winters snow will eventually wash the offending webs from the tree. You could manually remove the webs from the trees – but this can be difficult in a 50 foot tall cherry tree (a webworm favorite). July treatment with an insecticide will usually suppress this insect – unfortunately repeat applications are often necessary.