By now, you have probably noticed the spindly, white, webbed nests of the fall webworm emerging. Not to be confused with the eastern tent caterpillar. The nests of the webworm tend to be much larger and messier than that of the tent caterpillar. Also, the webworm weave their nests nearer to the ends of the branches, where as the tent caterpillar will form its nest in the nodes. While the fall webworm is generally harmless to healthy trees, those that are already compromised may suffer fatal defoliation if an infestation occurs.
The nests of the fall webworm serve as a temperature regulated cocoon for the webworm larva. Emerging in the late summer and early fall, be on the lookout for these thready webs.
The adult female moths will seek out deciduous (leaf-shedding) trees and lay their eggs on the undersides of leaves. They will lay several hundred at a time, in batches covered in fine threads. About a week later, the larva will hatch. These caterpillars are seen in colors varying from light yellow, to grey. They will have 2 light colored stripes on either side, with yellow spots and bristles.
In their early stages, the caterpillars will feed inside the web, on the top layer of the leaves. As they develop, they begin to consume the entire leaf. The voracious eater can defoliate an already compromised tree. After 4-6 weeks, the pupa emerge, to overwinter in the leaf litter and bark.
If the trees on your property are showing signs of these cottony cocoons, call your arborist right away! A population of fall webworm can quickly wreak havoc on the health of your trees. Critical defoliation results in insufficient energy production in that tree. In a weakened state, the tree may become susceptible to other diseases that can spread and affect an entire property. Manual removal isn’t usually a preferred method of containment. Due to their choice of web placement (the tips of branches), removal is often difficult or out of reach. Regular sprays are the most effective way to keep your property healthy! We here at Fox are committed to providing inclusive pest control options!