Gypsy Moth

Facts, Identification & Control

Scientific Name

Lymantria dispar

Appearance

The gypsy moth has four developmental stages – egg, caterpillar (larva), cocoon (pupa) and adult. Male and female gypsy moths look very different. The adult female moth is white and has wavy, dark bands that run from the front to the rear of the front wings. Adult females have a wingspan of about 2 inches, but can only fly short distances. The female’s body is stout and densely covered with a patch of golden-colored hairs located on her head. Female gypsy moths are also larger than males at 2 ½ inches long when mature. Male moths are only about 3/4 inch and have plain, brownish-gray wings with large, feathery antennae. The antennae, like many other species of moths, assist in locating females to mate with. Full-grown larvae are easy to identify since they are very large (about 2 ½ – 2 ¾ inches) with long hairs, five pairs of blue bumps at their front and six pairs of red bumps at the rear of their back. The females lay an egg mass containing an average of 400-500 eggs covered with hairs dislodged and stuck to the egg mass from the female as she lays the eggs.

Behavior, Diet & Habits

Gypsy moth caterpillars prefer hardwood trees and are known to feed on more than 300 tree species. However, their preferred tree species are oaks, apple, some poplars, willow, alder and hawthorn. Their complete life cycle is completed in one year. The caterpillars may completely defoliate trees by eating all of its leaves. Gypsy moth eggs hatch and the larvae begin feeding at a time of year when many of their host trees are beginning to obtain leaf growth, usually around the month of May. Feeding normally begins at treetop, so gypsy moth defoliation may not be seen on tall trees until the degree of defoliation becomes heavy. Younger caterpillars are usually feeding in the tops of trees and may go unnoticed on large trees. As the caterpillars age, older ones no longer remain in the upper regions of the tree, or the canopy, but move up and down the tree, seeking shelter sites on the ground and the tree trunk during the day and then moving back up the tree at night to feed on the leaves.

More Information

If a homeowner thinks they may have a problem with gypsy months, the first thing to do is contact your local extension service office for help in correctly identifying the pest. Treating the caterpillars with insecticides can be difficult for a homeowner, so always seek the advice of your pest management professional. Homeowners and government agencies sometimes use a bacteria called Bacillus thuringiensis to kill the insect’s larval stage. Tree banding using burlap, tape and sticky substances to trap larvae moving up and down the tree trunk usually captures a lot of caterpillars, but generally does not significantly reduce the overall population. Removing eggs masses by scraping them off the tree before the eggs hatch is also a good control measure.