Fall webworms active now

Fall webworm (Hyphantria cunea) nests are everywhere right now. Everything that makes a webbed nest is variously referred to as webworms, tentworms, and bagworms but these are not the same. Let’s start with the most wrong name: bagworms. Bagworm caterpillars each live in an individual bag that they cover with plant debris. The most common bagworm is (Thyridopteryx ephemeraeformis) which feed mostly on evergreens throughout the eastern US.

Fall webworms make a tent of sorts out of silk, but references to tents are best left for eastern tent caterpillar (Malacosoma americanum). These colorful caterpillars feed primarily on cherry and apple trees in early spring. They are gone by now. They make nests in the crotches of branches. As a result they are vaguely tent shaped.

Fall webworms, active now, make webs. Nothing tent like about them except that they can live inside. They are long messy structures covering the ends of branches, never in crotches. They are common in sourwood, pecan, hickory, and sweetgum but can infest many tree species. Recently I have heard reports from around the state of redbud and even crape myrtle.

Fall webworms do not usually cause severe damage to trees in terms of defoliation or reducing tree health. The main issue is cosmetic. The nice thing is that since nests are dangling at the ends of branches you can just prune and discard them. No chemicals or fire – which seems popular in some parts – necessary. It’s amazing how people get more concerned about a few caterpillars than their own safety.

(Please don’t burn insects. This includes webworms, tent caterpillars, and yes, even yellow jackets. It’s not safe, and it’s not legal.)

Fall webworm adults are active at night and lay green eggs on the undersides of leaves. Small yellow larvae hatch from the eggs and start building the silk nest for protection. They expand the nest to enclose more leaves for them to eat. This is why the nests get larger and larger. Larvae leave the nest to pupate in leaf litter or nooks and crannies of bark. The last generation of the year will overwinter as pupae.

2018-08-07T13:46:59-04:00 August 7th, 2018|Categories: Landscape IPM, Natural History and Scientific Adventures|Tags: , |

About the Author:

Steve Frank
I am broadly interested in the ecology and management of arthropod pests. Herbivorous arthropods cause extraordinary damage to plants in agricultural, urban, and natural ecosystems. Understanding interactions between pests and their environment, plant hosts, and natural enemies can improve management practices and reduce pesticide applications.