The variable oak leaf caterpillar periodically defoliates extensive
areas of hardwood forest in the eastern United States. Its range covers
all of the southern and eastern states as far west as east Texas. The
larvae feed primarily on oaks but will also feed on beech, basswood,
birch and elm. Other defoliating insects may be associated with
outbreaks causing additional damage. Young larvae skeletonize the leaf
while older larvae devour the entire leaf except the primary veins.
Infestations are generally more severe in the South, where the insect
has two generations per year causing two periods of defoliation in a
single year. While infestations usually subside before many trees are
killed, heavy defoliation reduces the tree’s growth and vigor.
[Illustration: Larva of the variable oak leaf caterpillar.]
The variable oak leaf caterpillar overwinters as a non-feeding larva in
a cocoon on the forest floor. It pupates and emerges as a moth the
following spring. The female moth, gray in color and about 1¾ inches
long, lays about 500 eggs singly on the leaves of host trees. The larvae
feed on foliage for five or six weeks, drop to the ground to pupate, and
emerge as adults in mid-summer. Larvae hatching from eggs laid by the
second generation of moths defoliate the trees for a second time during
late summer. By late October the mature larvae of the second generation
have dropped to the forest floor to overwinter. The full grown larva is
approximately 1½ inches long. Color varies among individuals. The head
is generally amber brown with curved diagonal white and black bands. The
body is usually yellow green with a narrow white stripe down the center
of the back bordered by wider dark bands.
Outbreaks of the variable oak leaf caterpillar may be severe but
generally subside before serious tree mortality occurs. Parasites and
predators are not effective in controlling rising populations of the
insect. Mice and predaceous beetles feed on the resting larvae and pupae
in the litter and soil of the forest floor. While no chemical is
currently registered for control of this insect, chemical spraying has
been effective and safe in controlling closely related insects.