Written by John Sepulveda, Certified Arborist WI-1454A
Known as the spongy moth, Lymantria dispar is an invasive species that is causing a lot of trouble for trees in North America. It was first introduced by accident when it escaped the lab of a scientist who brought it here to find a new silkworm in the 1860s. Since then it has spread from Massachusetts and reached as far west as Minnesota. Spongy moth is a particular problem as it feeds on over 300 species of trees and shrubs. Oaks are the most susceptible, but it will feed on birch, fruit trees, poplars and hawthorns. The caterpillar causes defoliation of the host tree. The adult moth does not eat.
Identifying Spongy Moth Caterpillars
The larvae grow to be about three inches long, are blackish and have many hairs as well as five sets of blue dots followed by six sets of red dots on their body. There are often many caterpillars present due to it not having any natural predators to keep them in check. They can cause defoliation rather quickly.
L. dispar in its adult form is brown with dark brown patterns for the male and nearly white with a saw-toothed pattern for the females. It should also be noted that the female does not fly. The female will lay eggs in a whitish-yellow sac that is easily identified. The sacs can be found on plants, firewood, cars, yard furniture - nearly any place out of doors.
The spongy moth is a pest that is currently being monitored closely by federal and state government agencies. It is highly recommended that before traveling from the quarantine zone to unaffected states, people check for the moth or its eggs on all firewood and vehicles. The goal is to slow the westward spread of the moth and save trees. In Wisconsin, the quarantine zone is about the eastern two-thirds of the state.
Hoppe’s certified arborists can inspect your trees for identification of spongy moth infestation and provide options on what to do next for your trees and shrubs. Hoppe’s Plant Health Care team of certified commercial pesticide applicators can manage the treatment plan. If you’d like to schedule an inspection, please give us a call at 414.257.2111 or request a quote.
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