Since then, much of lower Michigan has experienced at least one gypsy moth outbreak. This pest continues to spread into Wisconsin, Indiana and other North Central states. May. The caterpillars feed for six to eight weeks on the leaves of trees in forest, rural and urban areas. Oak trees are their favorite hosts, but the caterpillars also feed on aspen, willow, crab apple and at least 300 other trees and shrubs. Defoliation can be severe and may weaken or some- times kill trees.
Trees weakened by defoliation can become more susceptible to other pests.
A gypsy moth outbreak can be unpleasant for residents in an affected area. Large caterpillars are abundant, and may wander in search of cool, shady areas, often resting on the sides of houses and trees during the day. In addition, caterpillar droppings, known as frass, rain down on driveways and picnic tables. Some people experience skin or eye rashes or respiratory allergies when they are exposed to the hairs on the caterpillars. Most gypsy moth outbreaks typically last two to four years in urban areas, then collapse, usually because the caterpillars die from viral and fungal diseases.