Common Name: Gypsy moth
Scientific Name: Lepidoptera: Lymantria dispar
Status: A pest of hardwood trees
Damaging Stage: Caterpillar

Biology: Gypsy moths have wings with variable patterns or black spots and bands. Male have brown functional wings and feathery antennae. Females are cream-colored, have thread-like antennae and cannot fly. Gypsy moth larvae are dark-colored with five pairs of blue spots followed by six pairs of red spots. They are approximately two inches long when mature. Larvae have yellow and black head capsules and are completely covered in small hairs.

Caterpillars prefer oaks, but may feed on several hundred different species of trees. Female moths lay egg masses indiscriminately on trees, houses, and other structures in late summer. Often campers unknowingly spread this pest when egg masses are attached to recreational vehicles. Gypsy moths survive the winter in the egg stage and hatch in the spring when temperatures are above 60�F. Eggs are laid in mid- to late-summer. They complete one generation per year.

Injury: Heavy infestations can be responsible for the complete defoliation of host trees. This damage, however, does not directly cause death for these plants. Defoliation does leave trees susceptible to secondary organisms (borers, root rot) that successfully attack stressed trees and cause mortality. Caterpillars can also cause allergic reactions in humans. The hairs cause skin rashes, particularly during the month of May when larvae are small.

Action Threshold: "Moderate defoliation" is described as 31-50% loss of foliage. The number of caterpillars at this level must be controlled with a chemical option.

Management: Bio- and chemical control can suppress populations when applied early. Homeowners can also plant gypsy moth-resistant trees to replace damaged arbors.