Gypsy Moth

Lymantria dispar

Pest Rating: A

Lepidoptera (Moths and Butterflies)
Lymantriidae (Tussock Moths)
Heavy infestations occur in southeastern Canada, the eastern seaboard south to the Carolinas, and west to Michigan. Gypsy Moth has been sporatically detected in all of the contiguous United States.
Favored hosts include oak, birch, willow, poplar, apple, larch, lindon, alder, box elder, roses and sumac. However, many other deciduous and evergreen trees and shrubs are readily fed upon by older larvae. They have also been known to feed upon grasses and garden crops.
Nature of Damage:
The caterpillars or larvae of these moths feed upon the leaves of the host plant. Heavy infestations strip the trees of their foliage. Repeated defoliations of deciduous trees may kill them, while it may take only one defoliation to kill an evergreen tree. Any defoliation will seriously weaken a tree and increase its susceptibility to attacks by other insects and plant diseases. A defoliated forest allows sunlight to enter and dry out the soil and destroy the humus. This eliminates watershed and leads to potential fire hazard.
Egg: Laid in compact clusters which are protected and covered by brown body hairs from the abdomen of the female moth. A normal cluster contains 400 to 600 eggs, and is generally laid on the bark of the host tree, but is often deposited on any nearby object including fence posts, stones, vehicles, camping equipment and outdoor furniture.
Larva: Sooty grey in color, with long still brown hairs along the sides, and two rows of blue and red hairs along the back.; about 5 cm in length when fully grown; feeding mostly at night.
Pupa: Reddish-brown to dark brown in color; about 2.5 cm in length; usually found attached in a secluded area, such as the underside of branches, under lose bark, under vehicles, etc.
Adult: Gypsy Moths are sexually dimorphic, the male being quite different from the female. The male is around 2.5 cm in length, with a wingspan of 4 cm, light brown bodied with dark brown wings. The female cannot fly. She is about 2.5 to 3.5 cm in length, with a wingspan of 5.5 to 6 cm, and has a light buff body with white forewings. The female is merely an "egg-producing" organism and dies shortly after egg laying. Neither sex feeds in the adult stage.
Life Cycle
Stage Place Time of Year
Egg On trees, stone, vehicles, posts, etc. July to May (nine months)
Larva Foliage of host plant May to early July
Pupa Sheltered places 1st 2-3 weeks of July
Adult About host plants July to September
Generations Per Year:
Most Likely Way of Introduction:
Eggs transported on vehicles and other outdoor articles.
Inspection of Host Material:
Inspect surface of any item that has been stored or used outdoors in a Gypsy Moth infested area for egg masses. Check secluded surfaces (corners, cracks, inside poles, etc) closely. Larva and Pupa may also be found.
Quarantine Summary:
Federal Domestic Quarantine 301.45, CFAC 6305, CFAC 6461.5