GYPSY MOTH (GM): Lymantria dispar (Linnaeus) Order - Lepidoptera: Family - Lymantriidae

DISTRIBUTION: Canada, Europe, Asia, North Africa, northeastern United States (including portions of CT, DE, IN, OH, ME, MA, MD, NH, NJ, NY, PN, RI, VA, VT, WV, WI). Spot infestations occur in the states of WA, OR, northern CA, UT, and CO

DESCRIPTION:Eggs (Fig 3) are laid in compact clusters of 40-1000 covered with hair (setae) from the ♀s body. Egg masses are a light buff color but turn whiter with exposure. 1 st instar larvae (Fig 3) are mostly black and about 1/8” long. Young larvae are covered with long buoyant hair. Maturing larvae take on a sooty gray color with tuffs of “hair” coming from their sides. Late instar larvae (Fig 4) develop 5 pairs of blue dots and 6 pairs of red dots along their back and are about 3” long. Pupae (Fig 5) are bare reddish-brown to dark brown and are supported by a few silken strands.

Adults are moths. ♀s (Fig 1) are whitish with black marks 1-1 ¼” long with a wingspan of 2-2 ½”. Their forewings have several contrasting zigzag bands of black or dark gray scales. ♂ moths (Fig 2) are grayish brown, approximately 1” long with a wingspan of 1-1 ¼”. Their forewings have elaborate dark brown to black markings. Antennae are strongly feathered.

HOSTS: Larvae feed on more than 500 species of plants. Favored hosts are oak, alder, birch, willow, poplar, apple, aspen, box elder, roses, and sumac. Pine and spruce are readily fed on but less favored.

DAMAGE: Heavy infestations strip the trees of foliage. Trees may die, especially after repeated defoliation. Any defoliation increases susceptibility to insects and plant diseases, decreases watershed potential, and increases fire danger. Wildlife is displaced, usefulness is reduced for recreational areas, and management costs increase.

INSPECTION TIPS: Egg masses can be detected on RVs, and trailers from infested areas. Crawl under the vehicle (use mirror) and check the backside of the wheel wells, inside the bumpers, etc. Also inspect any other undisturbed crevices such as tire jacks and window frames. In suburban areas, egg masses are frequently found in woodpiles, rock walls, lawn furniture, behind shutters, and beneath lower rows of shingles. Burlap strips placed about 5’ up on the trunk of host trees are used to detect larvae on their way up the tree. Pheromone baited traps are used to detect moths.

LIFE CYCLE: GM has a one-year life cycle, overwintering as eggs. The larvae emerge late April or early May. Eggs in each mass hatch completely in 3-5 days but multiple masses take 2-3 weeks. ♂ and ♀ larvae go though 5 and 6 instars respectively. Each larval stage takes 4-10 days. Early stage larvae move to leaves to feed, produce silken stands and spread by “ballooning” (blowing in the wind). Late stage larvae feed at night and hide during the day on the tree or in the ground. If populations are high, they feed night and day. Larva pupate on the end of a silken strand in their hiding place. Pupation lasts about 2 weeks. ♀ moths do not fly and die in a few days. ♂ moths fly in a zigzag pattern often following the edge of woodlands and may live 2 weeks. Adults do not feed and are found July-Aug.

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