Pecan Webworms: Trunk Treatment for Tall Trees

Fall Webworm Biology

Webworms (Hyphantria cunea) build silken tents on branch tips in late summer/fall. Two generations/year; second (Aug-Sept) larger. They don't kill mature trees but reduce nut crop and aesthetics.

Control for Unreachable Canopies

Trunk Barrier Method (Best for Homeowners)

• Caterpillars descend trunk to pupate in soil/mulch.
• Tanglefoot on tree wrap (6″ band) traps them.
• Or spray trunk with acephate (Orthene)—systemic, longer residual than Sevin.
• Apply when webs appear (late summer).

Why Not Foliar Spray?

• Impossible coverage on 60+ ft pecans.
• Sprays harm beneficials (wasps, birds that eat webworms).
• Webs protect caterpillars from contact insecticides.

Alternative: Biological Control

• Tear open low webs with pole/stream of water → birds/predators enter.
• Bt (Bacillus thuringiensis) on reachable webs only.
• Never burn webs—fire hazard, tree damage.

Realistic Perspective

• Late-season defoliation doesn't impact current growth.
• May reduce next year's nut set slightly.
• Populations cycle naturally—big years followed by crashes.
• Trunk treatment reduces next year's local population.