The gypsy moth can now be found in every county in the lower peninsula and in certain areas of the Upper Peninsula. Gypsy moth caterpillars can be annoying, especially during outbreaks. Caterpillars are found munching on leaves of a variety of hardwood trees, including oak, birch, basswood and aspen. Unhealthy trees are weakened by defoliation. This makes them susceptible to other insect and disease problems that can kill such trees.
Healthy trees are far less susceptible to the effects of gypsy moth feeding.
Fertilize trees in the spring and fall, water them frequently during dry spells, and avoid mechanical damage and soil compaction to keep your trees in good condition. A healthy hardwood tree can be stripped of all its leaves two or three years in a row without being killed. Three to four weeks after defoliation, the tree will grow new leaves. Healthy trees reserve nutrients in their roots to replace those lost to leaf-eating insects such as the gypsy moth. Still, defoliation is a nuisance and, in some cases, a potential threat.