Fall Webworms in Houston: Identification and Management

Silken Tents on Tree Branches: Fall Webworm, Not a Parasite

Large gray webs enveloping branch tips on a West Houston tree in late summer are classic fall webworm (Hyphantria cunea) nests. Caterpillars feed inside, skeletonizing leaves, then expand the web as they grow.

Life Cycle Highlights

• Overwinter as pupae in soil, leaf litter, old nests.
• Adults emerge May–July (mid-March in South); up to 4 generations/year.
• Eggs laid in masses on leaf undersides; hatch in ~1 week.
• Larvae mature in 6 weeks, drop to pupate.

Damage Assessment

Late-season defoliation rarely kills healthy trees. Unsightly nests are the main concern. Multiple generations in long summers can cause significant leaf loss.

Control Options

Mechanical

• Prune out small nests in small/medium trees.
• Crush early nests (few leaves).
• Never burn—damages tree more than caterpillars.

Biological

• Bacillus thuringiensis (Bt) – Effective on young larvae. Use UV-protected formulation; spray leaves adjacent to nests so they’re eaten as web expands.

Chemical (Shade Trees)

• Malathion 0.25% (3¼ pts 57% EC / 100 gal or 1 Tbsp/gal).
• Sevin 0.25% (2½ lbs 80% WP / 100 gal or 2 Tbsp/gal).
• Wet nest and nearby foliage; larvae contact residue as they move.

Best Practice

Monitor early; treat only if aesthetic damage is unacceptable. Bt is preferred for safety and selectivity.