Although it has been a light infestation in the walnut tree this summer, our native fall webworms began their damage in early July. Small silken masses appeared at the terminal part of our walnut tree branches enclosing tree foliage, the larvae’s food source. As the larvae grew, so did the webs as the need for more food to support the growing insects.
The female fall webworm adult is a snowy white moth that emerges from pupation in leaf litter and beneath bark of trees and lays hundreds of eggs on the underside of leaves. Eggs hatch in a couple of weeks and larvae begin to spin their webs and feed and grow for several weeks.
Over a hundred species of trees in North America fall prey to fall webworms but in my yard, it’s always our lone walnut tree. Last year I raked the leaf litter beneath the tree where webworms pupate. I may have slowed the cycle but certainly didn’t stop it entirely.
In the north, there is only one infestation during the fall season but we can have two or more in Virginia. I can only hope we don’t have the heavy infestation we had last autumn where many trees were defoliated. Unsightly as it can be, fall webworms rarely threaten the life of a large healthy tree.
Insect pests in North America often originate in Europe and Asia but this is one pest that North America or Mexico accidently shared with the world. It is now a serious pest in all parts of the globe. Like insect populations everywhere, the population of fall webworms fluctuate a great deal over time. I believe conditions must be perfect for the fall webworm in Virginia at present for those unsightly nests are showing up more and more as I travel the roads and byways of Tidewater.
Ann Hohenberger, The Garden Club of Gloucester