(Lymantria dispar)

Photo 49: USDA APHIS PPQ Archive, Bugwood.org

Biology

• 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

Photo 50: USDA Forest Service

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

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

Control

• in BC, an aggressive program of trapping adults and spraying trees with a biological insecticide (Btk) in areas where the moth has been fou 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

Links

• History of the Gypsy Moth in BC. British Columbia Ministry of Forests and Range. (http://www.for.gov.bc.ca/hfp/gypsymoth/history.htm)
• National Invasive Species Information Center, USDA. (http://www.invasivespeciesinfo.gov/animals/eurogypsymoth.shtml)
• Canadian Forest Service, Natural Resources Canada. Gypsy Moth. (http://cfs.nrcan.gc.ca/factsheets/gypsy-moth)
• Minnesota Department of Natural Resources, Invasive species. (http://www.dnr.state.mn.us/invasives/terrestrialanimals/gypsymoth/index.html)
• Animal and Plant Health Protection Service, USDA. Gypsy Moth. (http://www.aphis.usda.gov/plant_health/plant_pest_info/gypsy_moth/index.shtml)