Hosts: Ponderosa pine
Symptoms/Signs: Adult pandora moths are very large and heavy bodied, about 2.5 to
4.0 cm long, with a wingspread of 7 to 11 cm. The forewings are brownish
gray and hindwings are light pinkish gray, each marked with a black dot
and a dark wavy line. The males are distinguished by having large, feathery
antennae. The globular eggs, bluish green to bluish gray, are deposited
in clusters of 2 to 50. Early instar larvae are about 5 mm long. They
have shiny black heads and black to brownish bodies that are covered with
short, dark hairs. Fifth instar larvae grow to about 6 to 8 cm long and
are brown to yellowish green. Pupae are dark purplish brown, 2.5 to 3.5
cm long, and have a tough shell.
The pandora moth has a 2-year life cycle. Adults emerge between
late July and late August. The moths mate and females deposit their
eggs within a few days. The egg stage lasts at least 40 days and
most larvae emerge in October. Larvae are gregarious and extremely
cold hearty. They feed in groups on the foliage on warm days throughout
the winter. Fifth instar larvae leave the host trees in late June
and enter the ground where they pupate. They remain in the pupal
stage for the next 12 to 13 months.
Effects: During outbreaks, defoliation can be
severe over large areas. Due to the 2-year life cycle, however, defoliation
occurs only during alternate years. Outbreaks on the Kaibab Plateau have
subsided without causing any lasting damage. However, some growth loss
and even mortality can occur especially if trees are severely stressed
from additional factors such as drought or heavy dwarf mistletoe infections.
Insects and Diseases: May be confused with sawfly
larvae and defoliation. However, sawfly larvae have smooth bodies,
are smaller, 18 to 25 mm long, and have eight pairs of leg-like
appendages on the abdomen. Defoliation caused by sawflies usually
occurs on an individual or small group of trees and is not widespread
like that of a pandora moth outbreak.