(This post originally published 8/26/19 and updated 7/16/21)
Authored by Mark Griffith, Former Jack Frost Landscape Designer, ISA Certified Arborist MA-5032AVA, Certified Horticulturist #2232
Webs in trees…. You may have seen them while you were driving, you may even have them in your trees. It’s the FALL WEBWORM. This unsightly little guy is a communal caterpillar. They live in groups in the webs that they form at the ENDS of tree branches. The fall webworm is known to feed on more that 100 species of forest and shade trees. In the eastern U.S., pecan, walnut, American elm, hickory, fruit trees, and some maples are preferred hosts; in some areas persimmon and sweetgum are also readily attacked. I have them every year in my River Birch (Betula nigra).
The initial reaction when you see webs in trees is “Oh man! I gotta do something about this! It looks horrible!” The reality of the fact is that this is a mainly “aesthetic” pest. That means that trees are seldom killed by the fall webworm. They can be defoliated by them though, but as the name fall webworm implies, they do this just before the trees are going to drop their leaves in the fall. Healthy trees can handle this happening and will recover just fine.
The key to identification is this: Fall webworm build their tent at the END of branches and usually are more ugly than harmful. Eastern tent caterpillars, which appear in the Spring, form their webs in the crotches of branches close to the trunk of the tree.
So there you have it. They’re ugly, but not harmful. If you see webs in trees, don’t waste a lot of effort and money trying to eradicate them.
Instead, welcome these Fall Webworms to your trees as a new food source for birds.