Gypsy Moth: Know the Facts
Gypsy moth is a name we hear more and more in some parts of northern
Illinois. Unfortunately, were not always hearing all the facts
that we should. This article will describe the pest in its various
life stages, so homeowners can know if they have this pest or something
else. Damage and preventative measures will also be outlined here.
Life Cycle and Description
The moth (the adult stage) is usually present in July and August.
The male moths are brown and tend to fly in zigzag patterns. The
female moths are white or cream colored and do not fly at all. The
female lays her eggs in masses, usually on branches and trunks of
trees. Egg masses can also be found on patio furniture, recreational
vehicles and other outdoor items. The egg masses are cream or buff
in color and about an inch or so in length. They are present from
July or August until the following May.
The caterpillars hatch out of the eggs around the time when many
hardwood trees are starting to leaf out (usually around May). The
caterpillars enlarge as they go through 5 or 6 growth stages (called
instars). Younger caterpillars are usually feeding in the top of
the tree and may go unnoticed on large trees. Older caterpillars
may move up and down the tree. Older caterpillars are very distinct
in their appearance. Long hairs protrude from the caterpillars
body and rows of colored "bumps" can be seen on the caterpillars
back. There are four pair of blue "bumps" followed by six pair of
red "bumps". Feeding by the caterpillars occurs in May and June.
The caterpillars mature in late June and early July, then enter
a pupal stage. During this time the caterpillars are turning into
adult moths. Pupae are dark and do not move. Pupae can be found
under bark, in crevices, in sheltered areas and even on the ground.
The insect remains in the pupal stage for 7-14 days and then emerges
from its pupal case as an adult moth.
Host Trees and Damage
Gypsy moth caterpillars prefer hardwood trees and will feed on
many different species (including, but not limited to oak, apple,
some poplars, willow, alder and hawthorn). The caterpillars are
defoliators; they eat the leaves of the host trees. Young caterpillars
eat small holes in the middle of the leaves, while older caterpillars
feed from the outer edge of the leaf inward.
What to Do?
If you suspect your tree has gypsy moth, contact your local University
of Illinois Extension office for help in correctly identifying the
pest. Gypsy moth is often confused with other leaf feeding caterpillars.
If it is confirmed that you have gypsy moth on your property, you
should call the local office of the Illinois Department of Agriculture.
They are the lead agency in mapping the movement of this pest and
trying to slow its spread in Illinois. If you find egg masses on
trees or outdoor equipment, you can scrape them off and destroy
them. Treating the caterpillars with insecticides can be difficult
for the homeowner, since caterpillars most often feed high in the
top of the tree. Treating may make it more difficult for the Department
of Agriculture to monitor the pest. Contact the local office of
the Illinois Department of Agriculture before attempting any treatment.
August - September 2000: Gypsy Moth: Know
the Facts | Flood Tolerant Trees | Saving
Seed from the Garden | Ideal Time for Lawn