Ever notice tiny web tents throughout your street trees in the late spring and summer? Those are called webworm, and they are a common problem for street trees in New Jersey. There are two types of webworm: a spring variety, which is called eastern tent caterpillar, and fall webworm. These worms can defoliate your trees and look very unsightly. For the most part, webworm will not kill your tree outright, but it will eat up a good portion of the tree’s leaves. In extreme cases or on very young trees affected by webworm, the tree can die, so proper diligence and removal will help to reduce the burden of webworm on your street trees.
Both webworm and eastern tent caterpillars are native to New Jersey and affect many varieties of trees. Species such as elm, black walnut, and sweetgum are favored by the pest. The insects are relatively easy to identify: they create large silky webs throughout the tree’s branches. Eastern tent caterpillar makes a tightly woven web between the branches of the tree and can be found in the spring. In contrast, fall webworm has a more loosely woven nest, and begins to appear in the late summer to early fall. Eatern tent caterpillars have a dark reddish color, with a single white stripe down the back. Fall webworms are yellowish black in color. Caterpillars from both species can be seen munching on the leaves. For fall webworm, there can be one to two generations that grow and develop over the late spring and summer.. The larvae will stay on the tree until they reach adulthood, when they will leave the tree to complete their life cycle. The caterpillar will do most of the damage on a tree as it grows.
Fall webworm caterpillars on a tree. Photo Credit: University of Connecticut
As previously mentioned, both species of webworms make your tree look unsightly and can defoliate your tree. However, in most cases, the destruction is caused late in the summer and won’t kill your tree outright. The tree will be able to bounce back over the winter months and regrow their leaves in the spring. If you begin to notice webworm or eastern tent caterpillar on your tree, you can scrape away any webs and sacs that you see. Depending on the height of your tree, the worm might be in the uppermost canopy. Remove as much of the infestation as you can, and bag up the worms, or take them to the park for the birds to eat as a special treat. Remove webworm nests first thing in the morning before the caterpillars leave to feed. This is the easiest method for removal, as well as being the most environmentally friendly, chemical-free option.
Eastern Tent Caterpillars munch on leaves in their nest. Photo credit: Natures Wild Things
So, while fall webworm and eastern tent caterpillars are not the prettiest tree nuisance, they aren’t likely to kill your tree. The defoliation caused by the two pests will just make it look a little bald during the summer months. The worms will over-winter away from the tree and the tree will regrow its leaves the following year. There are sprays that can kill both pests, however these are usually not necessary. We recommend contacting a licensed tree expert if you have questions about chemical treatments for webworm or eastern tent caterpillar. For more information about the webworm, especially its lifecycle, check out this interesting article from Bartlett Tree Experts. Both webworm and eastern tent caterpillar is yet another pesky insect to stay vigilant for as you watch your street tree grow!