Description of Damage
In the grand scheme of things, fall webworms do not do a tremendous amount of permanent damage, although the webs are definitely unsightly. Caterpillars feed on leaves inside the webs, gradually enclosing more foliage as they grow. Heavy infestations may defoliate a tree but rarely kill it. Over 100 species of trees play host to these voracious pests, but here in central Virginia, they seem to prefer nut and fruit trees, such as walnut, pecan, cherry and crabapple.
Control is not necessary; however, you may not be able to tolerate the unsightly mess. If you do decide to take action, mechanical control is best. When you can reach them, prune branches containing webs and destroy them. Chemical control must be done when webs and larvae are small, no later than July, but it is not necessary. If you are lucky, birds and other natural predators may come to your yard and do the job for you!
For more information, go to http://pubs.ext.vt.edu/2808/2808-1013/2808-1013.html