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Gypsy Moth

Characteristics:

  • Eggs: Females lay oval, beige eggs on branches, fences, and buildings in masses of 100-600 or more. Eggs overwinter and hatch in early April or late May.
  • Larvae: Young larvae/caterpillars are black or brown and about 6 millimetres in length. As they grow, bumps develop along their backs along with coarse, black hairs. The mature caterpillar grows up to 64 millimetres long and has 11 sections. Each section has two coloured spots; the first 5 pairs are blue while the last 6 pairs are red. Larvae feed on hard and softwood trees and shrubs. They are able to travel between trees on threads that they spin.
  • Pupae: After 7 weeks, larvae pupate and are protected by a dark reddish brown case.
  • Adults: Adult moths are fairly large; females are known to have a wingspan of 50 millimetres or more. The male is dark brown while the female is nearly white with wavy, blackish bands across her forewings.

Identifying infestations:

  • Defoliated trees: Larvae can eat the leaves from many deciduous and coniferous trees, but prefer oak, cherry, white birch, maple, alder, willow, elm and trembling aspen trees.
  • Silk ballooning of larvae: In the spring, you may see larvae’s silk ‘balloons’ as they are carried by the wind to reach other trees.

IPM Toolkit:

  • Preventive tools: Not applicable
  • Physical tools:
    • Scrape egg nests from surfaces.
    • Hand-pick and crush larvae and pupae.
    • Trap mature caterpillars by wrapping a 45 centimetre wide strip of burlap around the tree at chest height. Tie a string in the centre of the burlap and let the top of the burlap flip down over the bottom strip. The larvae will crawl between the two burlap layers to escape the sun’s heat. In late afternoon, lift the burlap and remove the larvae.
  • Biological tools:
    • Parasites like birds, beetles, wasps, and flies prey on the gypsy moth.
  • Least toxic chemical tools:
    • Apply Bacillus thuringensis (Organic Insect Killer also known as Bt.k.) according to label directions when larvae are present.