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How to identify it
- Nests are dense webs of silk that pull leaves and branch tips together and fill with bits of foliage and frass, often at the top of the plant.[1][2][3]
- Caterpillars are yellow to yellowish-green with a black head and reach about 3/4 inch before pupating inside the nest.[1][2][3]
- Adult moths are dull yellowish-orange with a wingspan of about 7/8 inch.[2][3]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Fall webworm | Fall webworm nests can be hard to tell apart from uglynest caterpillar nests; check the caterpillars and the host plant.[2] |
Where it lives
It is found across Canada and the northern United States, including Vermont, and in Illinois, where it is most common on pyracantha.[2][1][3]
Biology and life cycle
It overwinters as eggs laid on the bark of host plants; the eggs hatch as the leaves flush in spring.[2][1]
Larvae feed inside their nest from May to September and pupate there; there is one generation a year.[1][2]
Adults fly from late June to September and lay the eggs for the next year.[1][2]
Chokecherry is the main host, followed by pin cherry, black cherry and other hardwood trees and shrubs.[2][1]
Damage and signs
Health risk
It feeds only on plants; UVM, Manitoba Agriculture and Illinois Extension mention no risk to people.[1][2][3]
Control
Traps and physical control
With only a few nests, pull them out with the caterpillars and drop them into soapy water, or prune or crush new nests; this works best while the caterpillars are small.[1][3]
Pesticides
Insecticides are usually unnecessary since the damage is mostly cosmetic, and they only work if they penetrate the webbing.[3][1]
Common questions
- What are the dirty silk nests on my chokecherry?
- Likely uglynest caterpillar nests, dense webs of silk, leaves and frass with yellow, black-headed caterpillars inside.[1][2]
- Do I need to spray uglynest caterpillars?
- Usually not; the nests are ugly but cause little lasting harm, and removing a few nests by hand is enough.[1][3]
Sources
- University of Vermont Extension, “Beware the uglynest caterpillar (A. Hazelrigg).” www.uvm.edu/extension/news/beware-uglynest-caterpillar (accessed 2026-10-19)
- Manitoba Agriculture, “Ugly Nest Caterpillar (Archips cerasivorana).” www.gov.mb.ca/agriculture/crops/insects/ugly-nest-caterpillar.html (accessed 2026-10-19)
- University of Illinois Extension, “Uglynest Caterpillar (plant problem selector).” selectors.extension.illinois.edu/pathogen/uglynest-caterpillar (accessed 2026-10-19)
- iNaturalist, “Archips cerasivorana taxon page (order and family).” www.inaturalist.org/taxa/1392261 (accessed 2026-10-06)