If the weather warms up a bit, we could see eastern tent caterpillars (Malacosoma americanum) and forest tent caterpillars (Malacosoma disstria) hatching before the next forest health newsletter. These are both early spring caterpillars and hatch very soon after bud break.

Eastern tent caterpillars with pen. Web nests and caterpillars will be small at first.

Eastern tent caterpillar will make a web nest that can often be seen on wild black cherry along roadsides, although they also like to feed on crabapple, apple, and a few other species. Forest tent caterpillar does not make a web nest and prefers to feed on aspen and oak.

Trees that are severely defoliated will send out a 2nd set of leaves in June. Crushing the caterpillars, or pulling the webs out of the tree are both good control options. Pruning out the web nest is not necessary. Burning or torching the webs out of trees is NOT a good control option as it can kill portions of the tree, and it may start a wildfire.

Forest tent caterpillars. First instar, recently emerged from their eggs. Notice this caterpillar has no webbing.

Written by: Linda Williams, forest health specialist, Green Bay, (Linda.Williams@Wisconsin.gov), 920-662-5172.