Spongy Moth

Last Modified: April 01, 2025
Dark-colored, hairy caterpillar with five pairs of blue dots followed by six pairs of red dots lining its back crawling on a partially eaten leaf.

E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Bugwood.org

Spongy moth (Lymantria dispar dispar) is a destructive, invasive insect that poses a danger to North America's forests. The caterpillars feed on the leaves of more than 300 species of trees and shrubs, eventually killing them. Female moths lay eggs on many outdoor surfaces—stacked firewood, trailers, grills, lawn furniture, and toys. When people move these items to a new location, the spongy moth's eggs also move.

Native to Europe, the spongy moth first arrived in the United States well over a century ago. Today it can be found throughout the Northeastern United States where it has dramatically changed the landscape. Early detection is critical to limit the spongy moth's spread to new areas. If left unchecked, this pest can strip leaves and even kill trees, if severe defoliation persists for multiple seasons.

  • Egg masses (late summer, winter and spring)
    • Female moths attach egg masses to trees, stones, walls, logs, and household items, such as patio furniture, children’s toys, and lawn equipment.
    • Each egg mass contains up to 1,000 eggs and is covered with buff or yellowish “hair” (from the abdomen of the female).
    • Egg masses are about 1-1/2 inches long and 3/4-inch wide on average.
  • Caterpillars (spring)
    • Newly hatched caterpillars are black and hairy.
    • Older caterpillars are a mottled yellow to gray color with tufts of bristle-like hairs. They also have a distinctive color pattern along their backs with five pairs of blue dots followed by six pairs of red dots.
    • They are about 1-1/2 to 2-1/2 inches long when fully grown.
  • Adult moths (summer)
    • Male moths are brown with a darker brown pattern on their wings and have a 1-1/2-inch wingspan.
    • Females are nearly white, slightly larger, and have a 2-inch wingspan but do not fly. Their wings are marked with dark, saw-toothed patterns.
  • Defoliated trees
    • Infested trees may be partially or completely bare of leaves.
    • A heavily infested forest will have a barren, wintry look in the middle of the summer.

View photos of spongy moth and the damage it causes:

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Controlling Spongy Moth

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Kathryn Bronsky

Agriculturist

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