Fall Webworms and Eastern Tent Caterpillars

Fall Webworms and Eastern Tent Caterpillars

Oh, What a Web We Weave Once We Hatch to Feed

Fall webworm developed into adult moth
Fall webworm developed into adult moth.
(Photo courtesy of Jay Sturner)

By Bill Willis

October 11, 2016

Both fall webworms and eastern tent caterpillars develop into moths, spin webs, crawl around in trees, eat leaves, and can cause homeowners despair. Employees have seen webs from both kinds of these caterpillars near the lake and ball field. Despite some similarities, these caterpillars have some important differences.

Eastern tent caterpillars usually appear in North Carolina in the spring. Like their name implies, fall webworms are seen in late summer. The tent caterpillars eat crabapple, hawthorn, and flowering cherry trees. The fall webworm is a less finicky eater; they will eat almost anything with leaves, including more than 120 different species of deciduous trees including crabapple, ash, and sweet gum. In their search for food, the fall webworms may attack the same tree that the tent caterpillars did in the spring.

Control Measures to Prevent Damage to the Landscape

Tent caterpillar moth
Tent caterpillar moth.
(Photo courtesy of Andy Reago and Chrissy McClarren)

These caterpillars can cause problems for gardeners and homeowners as they ingest vegetation in gardens. Even moths can lead to problems, as they will eventually breed additional caterpillars. It’s important to remove the webs of both types of caterpillars early even if it means manually pulling or cutting the webs out. If left alone, the caterpillars could easily defoliate a small tree before moving on to another tree. This leaf loss will then weaken the tree by reducing the total photosynthesis. The webs act as a barrier to sprays, which is why it’s imperative to, first open up the webs to reach the foliage where the caterpillars may be hiding. The pesticide, Bacillus thuringiensis var. kurstaki (BT commonly sold as Dipel Dust), is a naturally occurring soil bacterium, that will kill caterpillars after they eat sprayed leaves. This substance will not harm birds or animals that might feed on the leaves or caterpillars and is safe around pets and humans.

(Members of Wildlife and Industry Together also contributed to this article).

Eastern Tent Caterpillars
The eastern tent caterpillars hatched on campus in late April. They built a protective web in the crotch of tree branches, leaving the web to feed.
(Photo courtesy of Bill Willis)
Eastern Tent Caterpillars
The web of the eastern tent caterpillars protects them from the weather and predators. They do not leave their web on cloudy or rainy days and at night.
(Photo courtesy of Bill Willis)
Fall webworms in a tree
Fall webworms hatched and created their web in August. These build their web at the ends of branches, enclosing leaves within the web.
(Photo courtesy of Bill Willis)
Webworms up close
Unlike the tent worms, webworms don't have a bright identifiable yellow strip. The caterpillars are active at different times.
(Photo courtesy of Bill Willis)
Fall webworms web in a tree
As the fall webworms feed, they spin their web larger and remain under the protection of the web.
(Photo courtesy of Bill Willis)
Fall webworm web removed from tree
A fall webworm web at the ball field that was removed from a sweet gum tree. By the time that caterpillar spins its cocoon, the nest is rather messy.
(Photo courtesy of Bill Willis)
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