Anisota senatoria (J.E. Smith)
Submitted by Dr.
James Robinson, Professor and Extension Entomologist,
Extension Center at Overton, Texas
IDENTIFICATION: Larvae of the orange-striped oakworm are
charcoal black with orange-yellow stripes. The head is jet black
and the segment just behind the head is bright orange-yellow. The
second thoracic segment (right behind the head) have long, black
spines. These spines or “horns” are used to scare predators
away and do not have the capacity to sting. The abdominal spines
are relatively small. The larvae, when mature, are about 1-½ " long.
They may be found in East Texas forests from August to October. There
is one generation per season.
The larvae are gregarious when they are small. When they reach maturity, they
become solitary. These older larvae are often seen crawling around on lawns
or the sides of houses, or feeding singly on foliage. After maturity, the larvae
burrows three to four inches into the soil to pupate and overwinter.
This insect may be found in large numbers on the various species
of oak. Infestations are usually localized, but defoliation may be
The moths emerge from June to August and lay their eggs in clusters on the
undersides of leaves. The adult moth is 1-1/4” long with wings closed.
They are reddish brown, translucent with a submarginal dark stripe and a white
spot on each forewing. Over a period of a month the female will deposit up
to 500 eggs in a single cluster on the underside of an oak leaf, usually on
the lower branches.
DAMAGE: Young caterpillars feed by skeletonizing the leaf
surface. Older caterpillars are defoliators and may consume all but
the leaf midrib. Defoliation usually occurs one branch at a time
when populations are small. Occasionally the insect reaches outbreak
Tree health is rarely affected by oakworm defoliation. Because the caterpillars
feed in late summer, most photosynthesis is complete and foliage loss has little
impact on the tree. Native predators and parasites usually help keep the insect
from being a problem every year.
CONTROL: Manually destroy aggregations of young larvae when
detected on small trees. An application of Bacillus thuringiensis
(Thuricide) or horticultural oil will control young larvae. Damage
is seldom widespread and chemical control is rarely needed.
QUOTE: Joe Pase,
an entomologist with the Texas
Forest Service at Lufkin has the quote of the day, “The
larvae are really doing homeowners a favor by converting leaves to
pelletized fertilizer for free.”