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Tussock Moth - Orgyia pseudotsugata
  
USDA Forest Service
Region 4 Archives
USDA Forest Service
www.ipmimages.org |
A. Steven Munson
USDA Forest
Servicewww.ipmimages.org |
Jerald E. Dewey
USDA Forest Service
www.ipmimages.org |
 HOSTS: Douglas-fir, all true firs and spruce. Also cottonwood.
DESCRIPTION:
First
instars are gray with long hairs. Later instars develop four dense
tussocks of yellow brown hairs on their backs. Mature larvae are up to
1 1/4 inches long, have two long dark tufts of hair just back of the
head, a longer tuft on the posterior end, four tussocks on their back
and the rest of the body is covered with short hairs radiating from
red, button-like centers. Adult male moths have rusty colored forewings
and gray-brown hind wings, with a wing span of about 1 inch. The adult
females are wingless and thick bodied.
LIFE
CYCLE: Eggs
overwinter in a mass covered with the gray hairs of the female. Eggs
hatch in late spring and caterpillars migrate to the new growth at the
top of the tree. Some are dispersed by the wind to new hosts.
Caterpillars first feed solely on new growth, then as the larvae mature
they move on to the older needles. Entire trees may be defoliated if
the populations are high. By late summer caterpillars are full grown
and may migrate away from the infested tree. They pupate in brownish
spindle-shaped cocoons. Adults emerge in mid to late summer.
CONTROLS:
Spiders,
parasitic wasps, and tachnid flies provide some natural control.
Extreme winters and freezing spring temperatures limit populations. Bt
can be used if larvae are newly hatched and still small. Add
insecticidal soap to Bt sprays. Pyrethrum plus insecticidal
soap if populations are high. See Bacillus thuringiensis.
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