Web-like nests of fall webworm caterpillars, are beginning to appear in parts of the state. The webworms are a common native pest active from July through September in Wisconsin. The fall webworm feeds on leaves of almost all shade, fruit, and ornamental trees and shrubs, except for conifers, throughout most of the U.S. and southern Canada. They typically form nests of loose webbing over the tips of tree branches.
DNR forest pest specialist Todd Lanigan in Eau Claire says the worms create a loose webbing around the branches that it is feeding on. He says as the caterpillars grow the webbing gets larger.
He says it's more of a cosmetic problem than a tree damage issue...
"....The defoliation that is occuring won't harm whatever plant that it's growing on unless it's a really small plant, recently planted, something like that. Then you might get some die back. Normally, the feeding damage does not hurt the plants at all...."
A rake or pole may also be used to roll up nests and remove them from the tree. Detached nests should be placed in a container of soapy water overnight to drown caterpillars You may also scrape the nests off onto the ground and crush them to destroy the caterpillars. These actions are best done in early morning or late afternoon when caterpillars are gathered in their nests. Lanigan says you can loosen up the webbing to let predators in, or take the rake, put them on the ground and step on them or put them in a bucket of soapy water.
He says if you use a pesticide, you should make sure the pesticide gets through the webbing to reach the caterpillars. These caterpillars are not related to the Forest Tent Caterpillar which are also native to Wisconsin but can be much more destructive.
