The gypsy moth, currently established in North America, is a European
native that was accidentally introduced into New England in the late
1800's during an attempt to rear an alternative silk producing insect.
Its current range extends from Maine to North Carolina and west
across Pennsylvania and into Virginia, West Virginia, Ohio, Michigan,
and Wisconsin. Spread occurs as a result of both natural flight of the
moth and the attachment and transport of egg masses on vehicles.
Gypsy moth is known to feed on over 300 trees and shrubs. Favored
hosts include oak, apple, alder, basswood, birch, poplar, sweet gum,
willow, and hawthorn. Less favored host species include hickory,
maple, cherry, cottonwood, elm, black gum, larch, sassafras, and
hornbeam. Some mortality even occurs in white pine. Many other
plants may be fed upon. The gypsy moth has one generation per year.
From June to mid-July, the female attaches buff-colored, velvety egg
masses to sheltered places on outdoor objects. These masses allow
the insect to overwinter and may contain up to 1,000 eggs. Masses are
also embedded with female abdominal hairs that may act as an allergen.
The eggs hatch in April or May. Young larvae chew small holes in
leaves, while older larvae consume entire leaves except for the larger
veins and midribs. The whole tree may be defoliated, resulting in
reduced growth and loss of vigor, as well as reduced aesthetic,
recreational, and wildlife values. If total defoliation is experienced
over several years, mortality may result. The older caterpillars are 1 1/2 – 2 1/2 inches long and are easy to identify by the tufts of hair on
each segment and the pattern of blue and red dots on their backs. The
gypsy moth pupates in dark brown pupal cases located in sheltered
locations. Male gypsy moths have a 1 1/2 inch wingspread with light
tan to brown wings marked with wavy, dark bands across the forewing.
Females are white, larger than males with a wingspread of 2 1/2
inches, and flightless. There is also an Asian strain of the gypsy moth
(AGM) that was identified in 1991. AGM has a much broader host
range and the females are active fliers due to their larger wingspan.
These factors would allow AGM to spread much faster than the
European strain and be even more damaging.