Eastern Tent Caterpillar vs Fall Webworm: Telling Rochester's Web-Making Pests Apart

By Linda Marsh, Pests & Diseases. Last updated: June 26, 2026

Every year around Monroe County, the same two questions land in our inbox. In May it is "there's a thick silk nest in the fork of my cherry tree." In August it is "the ends of my walnut branches are covered in messy white webs." These are two different insects with two different schedules, and confusing them leads to mistimed sprays and unnecessary worry. Here is how to tell eastern tent caterpillar from fall webworm at a glance, and when the webs actually matter.

What's the fastest way to tell them apart?

The single most reliable clue is when you see the webbing and where on the branch it sits.

If it is spring and the silk is tucked into a branch fork on a fruit tree, you are looking at eastern tent caterpillar. If it is late summer and the webbing is bagged over the outer leaves, it is fall webworm.

What does eastern tent caterpillar look like in Rochester?

Eastern tent caterpillar (Malacosoma americanum) is the spring web-maker, and it is native to New York. Adults lay shiny, varnished-looking egg masses around small twigs in summer, and the eggs overwinter right on the tree. When wild cherry, crabapple, and apple leaf out in April, the caterpillars hatch and immediately start spinning that classic tent in the first sturdy branch fork they find.

The caterpillars are dark with a distinct solid white stripe running down the back, flanked by blue and brown markings. They leave the tent to feed on nearby foliage on warm days and retreat into it for shelter, so the nest itself stays mostly free of chewed leaves. By June they are done feeding and the tents start to weather away. Because this happens early, a defoliated tree usually has the whole summer to releaf, and the NYS DEC's guidance on tent caterpillars stresses that the damage is mostly cosmetic on otherwise healthy trees.

What does fall webworm look like, and why does it appear so late?

Fall webworm (Hyphantria cunea) runs on the opposite schedule. You will not notice it until mid to late summer, when loose, dirty-white webbing starts engulfing the ends of branches on walnut, birch, cherry, and dozens of other hardwoods. The key behavioral difference: fall webworm caterpillars feed inside their web and keep extending it outward over fresh leaves, so the bag grows larger and messier all season.

The caterpillars are pale and densely hairy, tan to light green (sometimes nearly blue-black), with dark heads and tufts. By the time the webs are obvious in August and September, the tree is already winding down toward dormancy, so even heavy late-season defoliation has limited impact on a vigorous tree's energy reserves. The webs are unsightly more than they are dangerous.

Do these caterpillars actually kill trees?

For most established Rochester trees, no. A single season of spring or late-summer defoliation from these caterpillars is rarely fatal on its own. Healthy trees store enough reserves to recover, and the DEC notes that vigorous trees usually survive repeated defoliation. Both pests also tend to come and go in cycles rather than build year after year.

The exceptions are worth knowing. Repeated, heavy defoliation across consecutive years, or webs landing on a tree already stressed by drought, poor soil revealed by a soil test, girdling roots, or root disease, can tip a struggling tree into decline. If you are not sure whether your tree is merely hosting caterpillars or genuinely failing, our guide on why your tree might be sick walks through the difference. Defoliation stacked on top of those problems is the signal to escalate.

How should Rochester homeowners manage the webs?

For both pests, the safest option is mechanical. On reachable branches, prune out and bag the nests, or knock fall webworm webbing down with a strong stream of water or a pole so birds and predatory insects can get at the exposed caterpillars. Do not burn the nests in the tree: torching webs causes far more bark and wood damage than the caterpillars ever would.

Resist the urge to blanket-spray. Broad insecticides knock out the parasitic wasps and predators that naturally keep these caterpillars in check, and they are usually overkill for a cosmetic problem. If a young or recently transplanted tree is being heavily hit and you want intervention, a targeted, correctly timed treatment by a professional is the right call. For oak trees stripped by a different springtime defoliator, see our separate writeup on spongy moth in Upstate New York, because that pest is managed differently and on its own calendar.

When should you call an arborist instead of handling it yourself?

Call a certified arborist when the nests are too high to reach safely, when the same tree is being defoliated several years running, or when webbing shows up on a tree that is already declining. A professional can confirm the species, rule out look-alikes, and decide whether any treatment is even warranted. If you want a trained eye on it, you can schedule an arborist evaluation with Monster Tree Service. Our breakdown of when to call an arborist about tree insects covers the warning signs that move a bug problem from "watch it" to "get help." Climbing a ladder with a pole saw to chase caterpillars is not worth the fall risk.

FAQ

Are tent caterpillar and fall webworm webs dangerous to my tree? For a healthy, established tree, both are almost always cosmetic. They defoliate branches but rarely cause lasting harm in a single season. The risk rises only with repeated heavy defoliation or when the tree is already stressed.

It's August and there are webs on my branch tips. Which pest is it? Late summer plus webbing at the ends of branches points to fall webworm. Eastern tent caterpillar is finished by June and builds its nests in branch forks, not at the tips.

Should I spray insecticide on the nests? Usually no. Broad sprays kill the natural predators that control these caterpillars and are overkill for a cosmetic issue. Mechanical removal is safer, and a targeted professional treatment is reserved for heavily hit young trees.

Can I just burn the webs out of the tree? No. Burning nests does far more damage to the bark and living wood than the caterpillars would, and it is a fire hazard. Prune and bag reachable nests or knock them down with water instead.

Is this the same insect that strips oak trees in spring? No. Oak defoliation in spring is usually spongy moth, a different pest on a different calendar. See our spongy moth guide for that one.

Sources

• Monster Tree Service of Rochester
• New York State DEC: Tent Caterpillars
• Cornell Garden-Based Learning
• USDA Forest Service: Urban Forests