The little worms hatch in April or early May from egg masses laid on the trunks of trees by the adult moths the previous July. Egg masses are also deposited on houses, mailboxes and lawn furniture. As the caterpillars eat, they also defecate. As the frass from thousands of worms falls to the ground, the sound resembles rain falling through the forest canopy. Defoliation does not normally kill the tree, but it does seriously weaken it.
Weakened trees are more susceptible to disease and other insect damage.
If the tree is repeatedly defoliated over the course of a few years, it will die. Gypsy moth caterpillars can be controlled. This bacteria is a natural enemy of the Gypsy Moth caterpillar and is not harmful to people, animals, birds, or honey bees. When ingested, the bacterium produces a crystal protein toxin that kills the cells in the lining in the insect's digestive system. May. Some birds love to lunch on the Gypsy Moth caterpillar.