Gypsy Moth |
Gypsy Moth
The gypsy moth is found in every county in Michigan's
Lower Peninsula and in certain areas of the Upper
Peninsula. When feeding, the gypsy moth caterpillar can
leave trees stripped of foliage. Caterpillars eat leaves
of several hardwood trees including oak, birch, basswood,
apple and aspen. Unhealthy trees are weakened when
defoliated, making them susceptible to other insects and
disease problems that can kill them.
Gypsy moth eggs are laid in fuzzy, buff-colored
clusters during July and early August. Each cluster
contains 50 to 1,000 eggs. The female deposits these egg
masses on any convenient surface, including the bark of
trees, the underside of cars and trailers, on picnic
tables and on rocks and twigs. The gypsy moth over
winters in the egg stage until the following May. Gypsy
moth eggs are quite cold-resistant and can survive
temperatures as low as -20 f. The eggs begin to hatch in
May. Hatch occurs earlier if the weather is unusually
warm. The tiny black gypsy moth larvae begin crawling
into tree tops, attracted by overhead light. They can
disperse in the wind, first dropping from branch tips by
single strands of silk, then sailing through the air when
caught by a strong gust of wind. Long body hairs enable
them to travel up to a few hundred yards.
Following this dispersal period, small larvae feed
during day and rest at night. As they continue to grow,
the larvae develop five pair of blue spots and six pair
of red spots on their upper side. They begin feeding at
night and resting during the day in bark crevices on the
trunk and branches. At the end of this feeding period,
which lasts from about four to six weeks, the larvae are
about two inches long.
During the pupal stage, the gypsy moth begins to
transform from a larva to an adult gypsy moth. The dark
brown pupal cases hang in clusters, attached to the base
of branches, in tree crotches, and in bark crevices. The
insect is immobile during this stage and does not feed.
It remains in this form for about 10 days.
The adults emerge, leaving the pupae cases behind,
and begin to search for mates. The tan male moths are
about an inch long and are strong fliers. The males
search for female moths in a rapid zig-zag pattern.
female moths are larger, white, and cannot fly. Females
emit a potent sex attractant which lures the male moths.
Eggs are laid shortly after mating, often on tree trunks.
The adult gypsy moth does not feed.
There are two broad categories of methods to reduce
the number of annoying, large caterpillars and to help
trees live through gypsy moth feeding: 1) reducing or
limiting caterpillar numbers; 2) keeping trees healthy
through preventive maintenance.
Reducing Caterpillar Numbers
Gypsy moth caterpillar numbers can be reduced using
mechanical means. Remove egg masses by scraping them off
trees and other objects and dropping them into a soapy
water solution and burying them. Reduce large caterpillar
numbers by tying a band of burlap or denim or other dark
cloth around the trunk of a tree. Then fold half the
material over the string to give the caterpillars a place
to hide. The caterpillars hiding under the cloth can then
be swept off into soapy water and killed each day.
Caterpillars can also be reduced using biological
controls. Many formulations of the bacterium, Bacillus
thuringiensis variety kurstaki ("Bt" for short), are
available for use. Materials such as Dipel, Thuricide,
Sok Bt, Foray, etc., are among commercial names for
formulations of this biological insecticide. The
material should be used when larvae are less than one
inch long. A commercial applicator may be needed with the
proper equipment to apply it to large trees.
Egg parasites also reduce caterpillars. An example is
a tiny wasp that has about four generations during the
early fall and late spring. The wasp lays its eggs inside
the gypsy moth eggs. On sunny days in late summer and
fall, the small, black wasps can be seen walking and
buzzing on the gypsy moth egg masses. Egg masses that
show such activity can be scraped off trees, attached to
tape and placed on trees in your yard that have egg
masses you can't reach to scrape off.
Trees can be watered and fertilized to help prevent
caterpillar feeding from seriously harming them. During
the growing season trees should receive about 1 inch of
water per week. Tree fertilizers can be applied during
the fall as well. Trees that are not susceptible to gypsy
moth feeding can also be planted. Ashes, sycamores,
maples, hickory, dogwood, mountain ash, rhododendron,
locust, holly, cedar, walnut, butternut, juniper,
honeysuckle and most conifers are largely ignored by
gypsy moth and can be used in landscaping as a long-term
method of minimizing future gypsy moth problems.
For further information about gypsy moth, including
color illustrations of various life stages, and what to
do in woodlots or around the home, see Extension Bulletin
E-2302, "The Gypsy Moth in Michigan."
For more information on this and other pest problems,
check with your Extension Service county office, just look
in the white pages under county government. |
This information is for educational purposes only. References to
commercial products or trade names does not imply endorsement by MSU Extension
or bias against those not mentioned. This information becomes public property
upon publication and may be printed verbatim with credit to MSU Extension.
Reprinting cannot be used to endorse or advertise a commercial product or
company. This file was generated from data base 02 on 02/27/01. Data base 02 was
last revised on 12/04/98.
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