These nests are a group effort, spun by the caterpillars to protect them as they feed on the leaves of trees. Within a single nest, there may be dozens of caterpillars feeding. As they consume more and more leaf material, the caterpillars get larger and larger, and the nests expand accordingly.
While these nests may be considered an eyesore, the fall cankerworm does not cause serious damage to trees. Defoliation is often not extensive and although outbreaks can occur, they very rarely have long-term impacts. Fall webworms feed on several types of hardwood trees, but they prefer pecan, persimmon, sourwood, black walnut and sweetgum.
Because damage is not extensive, management is not generally recommended. Should you want to do something, however, the simplest option is to manually remove the areas of the tree encompassed by webs and destroy the webs and caterpillars. Chemical options are not usually recommended unless done very early in the summer when caterpillars and webs are small. Spraying at this time often does little to control caterpillars and existing webs. Alternatively, you can enjoy the haunting look it might give the area and stock up on candy for October.