Tree Killers: European Gypsy Moth

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  • Common English name: European Gypsy Moth
  • Other names:
  • Latin (scientific) name: Lymantria dispar

Threat type

150x150 insects

History in Canada

  • introduced from Europe to North America (Massachusetts) in 1869 for possible silk production
  • now well-established in the eastern US as well as small populations in western US
  • in Canada, it is most abundant in Ontario and Quebec
  • also occurs in small numbers in New Brunswick, Nova Scotia, and British Columbia
  • in BC, aggressive monitoring and control have prevented the moth from becoming established but introductions of egg masses from the east occur regularly


  • the female moth is mostly creamy-white with some dark markings and a wingspread of up to 62 mm (2 ½ in)
  • the male is darker and smaller with a wingspan of 37-50 mm (1 ½-2 in)
  • the female cannot fly so lays a single egg mass close to where she has emerged after pupation
  • each egg mass contains up to 1500 eggs
  • egg masses are laid on trees, rocks, or manmade objects, such as tires, trailers, or firewood
  • the species is easily spread when these objects are moved prior to the eggs hatching
  • eggs hatch in early spring and the caterpillars feed until mid-summer
  • the caterpillars are hairy with two rows of large spots on the back: red spots at the head end and blue spots at the tail end
  • caterpillars grow to 60 mm long (2 ½ in) when mature
  • Gypsy moths have one brood per year and overwinter as eggs
  • populations tend to cycle over the course of several years, going from abundant to rare and back

Impact on Trees

  • larvae can eat over 500 species of trees and shrubs but prefer oaks and poplar
  • trees can be completely defoliated when larvae populations are high
  • several years of defoliation can kill a tree

What can be done to control this tree killer?

  • in BC, an aggressive program of trapping adults and spraying trees with a biological insecticide (Btk) in areas where the moth has been found has prevented establishment
  • aerial and ground-based spraying of Btk as well as chemical insecticides to kill the larvae have been used in eastern Canada
  • there are several parasites and birds that attack the larvae

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