Gypsy Moth: Know the Facts
Gypsy moth is a name we hear more and more in some parts of northern
Illinois. Unfortunately, we’re 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
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 zig-zag 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 five or six 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 caterpillar’s
body and rows of colored “bumps” can be seen on the caterpillar’s
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. Treatment may require
the services of a licensed arborist.
For more information on gypsy moth, go to www.urbanext.uiuc.edu/gypsymoth/
June/July 2004: Prevent Garlic Mustard
from Setting Seeds | Gypsy Moth: Know the Facts | Wetlands
and Mosquitoes | Understanding Herbicides
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