By AL KNOX

For those of you who have lived in the area for over ten years, you may remember the forest leaf defoliations caused by gypsy moths in the early 1990's. The last peak defoliation in Pike County was in 1993, and gypsy moth populations collapsed after that data. The summer of 2000 has brought increasing concern by area residents over the caterpillars infesting the rural forested areas in the county.

Before choosing to resort to chemical controls of the caterpillars, you should determine if the caterpillars are gypsy moths or some other forest caterpillars. If they are gypsy moths, determine whether they are still a viable population or if they have been killed by the gypsy moth fungus (Entomophaga maimaiga), a natural fungus that attacks the caterpillar stage.

Gypsy moth eggs hatch in the spring of the year about the time the tree buds open. The small caterpillar is black in appearance and goes through several stages, or instars, before reaching the prominent coloring and characteristic of the adult gypsy moth caterpillar.

An adult caterpillar, the larvae stage of the moth, is usually found on the trees in late May, June and July and reaches about two inches in length. The body markings are distinctive with five pairs of blue spots followed by six pairs of brick-red spots on a black body. The caterpillar is hairy in appearance. It is at this stage that gypsy moths cause the most damage by doing what comes naturally-eating leaves. It generally takes three years of defoliation to kill a tree; however, defoliation creates stress on the tree, which, combined with other factors like drought, can kill the tree sooner.

Male gypsy moths are brown; female moths, which do not fly, are white with small brown markings. By late July and August, the moths have mated. The female lays egg masses on the tree trunks in late summer, and the egg masses over-winter on the trunks. The buff-colored egg masses are circular or oval in shape. They range in size from about dime-size to half dollar size.

Gypsy moths prefer oaks as their host tree species but other trees and shrubs can be defoliated when the preferred host is not available and the populations are high. Ash, poplar, locust, sycamore and black walnut are usually not attacked.

This summer in Pike County, many residents are finding that the gypsy moth fungus that attacks the adult stage is killing populations of gypsy moth caterpillars. Caterpillars killed by the fungus can be identified as follows: Bodies of the dead caterpillar will be attached to the tree trunk vertically with their head pointing downward; the dead caterpillar will be covered with fungal growth for a short time and then will become withered and brittle.

Similar leaf defoliators found in the area include the forest tent caterpillar and the eastern tent caterpillar. The eastern tent caterpillar is often mistaken for the gypsy moth. The caterpillar is black in color with a white stripe along the middle of the back and a row of pale blue oval spots on each side. Unlike the gypsy moth, the eastern tent caterpillar can be readily identified by the tent (web-like structure) that it constructs in the forks of tree branches. The eastern tent caterpillar is most often found on apple, wild or ornamental cheery, hawthorn, beech and willow.

Forest tent caterpillars, found usually in sugar maple, oak, black gum, and aspen, do not build "tents." These caterpillars are similar in size to the gypsy moth caterpillar but marking and color are different. Forest tent caterpillars are black-to-gray in color with a row of 10 to 12footprint-shaped markings white in color down the middle of the back.

Another leaf disease that may, at first, look like gypsy moth defoliation is an Anthracnose. This disease found primarily in sycamore, oaks and maples does cause foliage to look thin and causes yellowing of the leaves left on the tree.

None of the above causes the extent of defoliation that healthy and viable gypsy moth population can create.

For additional information on gypsy moths or other forest caterpillars, contact the Pike County Conservation District, HC 6 Box 6770, Hawley, PA, call 570/226-8220 or e-mail or pikecd@ptd.net.

[Al Knox is the Pike County Conservation Director.]