Integrated Pest Management Guide

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GYPSY MOTH, Lymantria dispar (L.)

Pest Status: The gypsy moth has not been found on cranberries in British Columbia. It is presented here because it occurs sporadically on deciduous trees in southwestern British Columbia. Local monitoring, using pheromone traps, is done by the Canadian Food Inspection Agency every year in southwestern British Columbia.

Life cycle and feeding habits: In Eastern Canada, this pest is known as a voracious feeder. On cranberry, the young hairy larvae attack the terminal buds first and, as the new growth develops, devour the leaves, flower buds, and blossoms. When very abundant, they also attack the old foliage. Young larvae feed mainly at night but mature larvae feed day and night.

The insect overwinters in the egg stage. Hatching occurs in late April and may last to late May, depending on the weather. Newly hatched larvae are typically hairy and about 2 - 3 mm (1/8 inch) long. Mature larvae are up to 6 cm (2.5 inches) long. Mature larvae are very distinctive, with two rows of large spots along the back usually arranged in five pairs of blue and six pairs of red from head to rear; many long hairs cover the body. Larvae have three pairs of front legs and five pairs of hind legs. They are usually found feeding on tree foliage or, in early instars, hiding in shady spots. Small larvae may be blown by the wind to new locations, assisted by their light, hairy bodies and long silk threads.

Once feeding is complete, most larvae move to protected locations, such as bark crevices, to pupate. The pupal stage lasts on average 2 weeks and occurs in July. Moths start emerging in late July and early August, peaking in the second to third week of August.

The male moth is tan to brown with irregular black wing markings and plumose (feather-like) antennae. Males have a wingspan of 3.7 - 5 cm (1.5 - 2 inches) and are strong fliers. Females are often larger than males with a wingspan ranging from 3.7 - 6.2 cm (1.5 - 2.5 inches). Females are whitish with faint darker and wavy bands across the forewings. Despite having full-size wings, the female European gypsy moth cannot fly. She emits a pheromone to attract the highly mobile and responsive males. Adults do not feed, and live for several weeks. After mating, indiscriminate laying of a single egg mass per female occurs from late July to September. There is only one generation per year.


Gypsy moth larva


Gypsy moth male and female