Eastern Tent Caterpillar
Eastern Tent Caterpillars form silk-webbed nests in
branches or where main stems fork. The colony uses the
nest for protection against predators and the elements.
The nest is built in layers. As the caterpillars increase
in size they add additional layers of silk to the nest.
Eastern tent caterpillars generally attack understory
trees, particularly crabapple, wild cherry, and apple, but
also will feed on peach, pear, plum, rose, hawthorn, and
others. The larvae often eat all the leaves off a tree.
Although this damage is unsightly and worrisome, it
usually only weakens the tree after three or more years of
more than 50% defoliation.
The caterpillars are hairy, black with white stripes
with narrower brown and yellow line on the sides and blue
spots. When full grown, they are about two inches long.
Caterpillars are the only stage which cause feeding
damage. After about six weeks of feeding and growing the
young spin white or yellowish white cocoons, about one
inch in length.
Adults are reddish brown moths with stripes on the
forewings and have a wingspan of 1" - 1 1/2". The adults
mate and females lay about 200 eggs in a ring around
twigs, laying on a foamy secretion which dries to a hard,
protective shell. The eggs overwinter and hatch out as
tiny larvae in early spring usually early to mid April.
If you have potential tree hosts, careful observation
and hand control may be all you need. In fall, winter, and
early spring look for egg masses and cut or scrape them
off and either burn or soak them in soapy water. In early
spring, tear out nests by hand or with a garden tool and
destroy the young caterpillars. This can be easily
accomplished by dropping the nest parts and caterpillars
in a pail or dishpan of soapy water. People often burn the
nest out of the trees, but we do not recommend this method
because of the safety hazard.
There are several natural enemies of the tent
caterpillar. A parasitic fly attacks full grown
caterpillars. This fly looks like a housefly, but is twice
as large, has a light gray thorax with three black
stripes. The fly maggot consume the caterpillar internally
and kill it as a pup (cocoon). That tent caterpillar may
have eaten your tree leaves, but it won't leave young to
do it next year. Ground beetles and predaceous wasps also
eat tent caterpillars, as do various birds, most notably
Northern orioles. The birds' hanging sack-like nests mean
you won't have to worry about tent caterpillars; orioles
have been known to eat entire infestations.
Acephate, carbaryl, malathion, and B.t. are the
recommended insecticides.Bacillus thuringiensis (B.t.) is
the most environmentally sound solution. If you own an
orchard, try to clear out nearby wild cherry trees, if
possible. If your trees have been defoliated, water and
fertilize them. One inch of water, applied once per week
is recommended.
For a complete listing of suggested control options
for all home, yard and garden insect pests, check with
your local Extension Service, found under local government
in the phone book.
Read and follow instructions on the pesticide label.
Heed all warnings. Check with your physician if you have
any concerns regarding your personal health risk.