Delta Journal
by Bob Thomas

Fall webworms (Hyphantria cunea) are members of the tiger moth family. Webworm caterpillars are small and green with black spots and long white hairs along the sides, while the adult moths are whitish, often with dark spots, and measure less than two inches from open wing tip to wing tip.

Webworms are appropriately named. Soon after hatching from eggs laid on the lower surface of leaves of their food plants, the very social larvae begin the construction of a silken web that, as the family matures, may encompass an entire branch. This is commonly seen locally on pecan trees, elderberry, and mulberry, though they will also feed on other deciduous trees.

In the north, webworms produce only one brood and are active strictly during autumn. The moderate temperatures of the south, however, allow the “fall” webworm to become active in the spring, thus producing more than one brood per year.

After shedding its skin five times, a webworm leaves the web in late autumn and forms a cocoon, usually in leaf litter on the ground or under loose bark. The adult emerges in the spring and the whole cycle begins anew.

Predators include parasitic wasps, birds and hornets.

The only other web-forming caterpillar in southern Louisiana is the eastern tent caterpillar (Malacosoma americanum). This species constructs its web in the forks of limbs rather than at the ends of branches like the fall webworm. Why? Because tent caterpillars leave the web to feed, using the web only as a refugium, while webworms feed on leaves enclosed by the web.

Under natural conditions, the webworm webs do not significantly harm trees, but many people complain that they are unsightly.