By Justin Fellenbaum
County Extension Coordinator
If you have noticed large, white webs covering the ends of tree branches around your yard lately, you are not alone. Fall webworms seem to be everywhere this time of year. While these webs can make an otherwise healthy tree look alarming, the good news is that fall webworms are usually more of a cosmetic nuisance than a serious threat to established trees.
Fall webworms (Hyphantria cunea) are native caterpillars found throughout Georgia. They feed on a wide variety of trees and shrubs, including hickory, persimmon, sweetgum, birch, oak and many fruit trees. They are particularly noticeable in late summer and early fall when their large silk webs begin appearing around the ends of branches.
The caterpillars construct their webs as they feed, gradually expanding the web to cover more foliage. Unlike some other caterpillars, fall webworms remain inside the web while feeding. As they mature, they leave the web and eventually pupate in protected locations. Several generations may occur during the growing season.
Will fall webworms kill my trees?
One of the most common questions homeowners have is whether fall webworms will kill their trees. In most cases, the answer is no.
Healthy, established trees can generally tolerate the amount of defoliation caused by fall webworms, particularly because the feeding occurs late in the growing season. Deciduous trees are already preparing for dormancy, and losing some leaves at this point in the season generally has little long-term effect on a healthy tree. However, young trees, newly planted trees or trees that are already stressed may be more susceptible to damage from heavy infestations.
For most homeowners, the biggest problem with fall webworms is simply how unsightly they are.
What should you do if you find them in your trees?
If the webs are within reach, one of the simplest options is to physically break them apart using a long pole or similar tool. This exposes the caterpillars to birds and other natural predators. On smaller trees, infested branches can also be pruned out and discarded.
Insecticides are rarely necessary for healthy, mature trees. If treatment is warranted because of a severe infestation or a particularly valuable young tree, control is generally most effective when the caterpillars are young and the webs are still small. Because the web protects caterpillars, simply spraying the outside of a large web may not provide good control.
Homeowners should always read and follow the pesticide label when using any insecticide and make sure the product is labeled for the particular plant and pest being treated.
It is also important not to confuse fall webworms with eastern tent caterpillars. Eastern tent caterpillars are primarily a spring pest and construct their webs in the crotches of branches. Fall webworms appear later in the year and build their webs around the ends of branches.
While it may be tempting to eliminate every web in sight, remember that fall webworms are a native part of our ecosystem. Birds, spiders, predatory insects and parasitoids all help keep their populations under control.
If you see fall webworms in your yard this summer, don’t panic. On a healthy mature tree, a few unsightly webs are usually nothing to worry about. Break up the webs if they are easily accessible, prune them out if appropriate, and otherwise let nature take its course.
If you are unsure what insect is affecting your tree or have concerns about significant defoliation, contact the local UGA Extension office for assistance. The Pickens office is located at 68 D.B. Carroll St., Jasper GA 30143 706-253-8840.
