Michigan Department of Natural Resources is forecasting another bad year for gypsy moth activity and tree defoliation following elevated populations in parts of the lower peninsula last year.
Gypsy moth is an invasive pest which was first discovered feasting on the leaves of Michigan trees in 1954. The caterpillars feed on a variety of tree species, but tend to favor oaks, aspens, and maples. A large population of caterpillars can significantly defoliate a tree in a matter of just a couple weeks and rain frass (caterpillar droppings) onto people and property. This feeding is typically concentrated from May to July.
Thankfully, even severe defoliation rarely leads to the death of an otherwise healthy tree, as they are usually able to produce a new batch of leaves in the summer to last the remainder of the growing season. The population of gypsy moth tends to undergo natural fluctuations. As the species gradually becomes more abundant, they compete for resources and live in closer proximity to one another. This leads to greater spread of pathogens, which kill the gypsy moth caterpillars.
After a significant die-off due to disease, gypsy moths live in lower densities in the following years, which leads to less spread of disease and the numbers start to rebound. Thus, the fluctuating cycle continues. Because this disease cycle largely keeps the population in check nowadays, a widespread gypsy moth control program is typically unnecessary. However, homeowners dealing with gypsy moth on their own property are encouraged to kill the caterpillars by squashing them or spraying them with a solution of dish soap and water. Just be careful not to kill any of our beneficial native