The eastern tent caterpillar can be a serious pest on cherry, plum,
peach, pear, and several other deciduous shade trees. These caterpillars
do not feed on evergreens. The preferred host is native black cherry
(Prunus seratina), which commonly grows on roadsides and
hedgerows. Nests of the eastern tent caterpillar are unsightly and
the repeated defoliation they sometimes cause can result in a decline
of the host, predisposing it to damage from disease organisms and
other insects. A single season's defoliation will seldom kill an
otherwise healthy tree, as the feeding occurs early enough in the
season for the trees to grow new leaves.
Larvae vary in size from 10 mm (3/8 inch) upon hatching to 50
mm (2 inches) long when fully grown. The caterpillars are primarily
brown and are thinly covered with light brown hairs. A white stripe
on the back is bordered with reddish-brown stripes and a row of
oval blue spots. The adult moths are brown with a wingspan of about
45 mm (1 3/4 inch). Two narrow, lighter-colored bands may appear
on the first pair of wings.
Egg masses of the eastern tent caterpillar may be found on smaller
twigs of infested trees. The dark brown, shiny egg masses are about
20 mm (3/4 inch) long and 12 mm (1/2 inch) in diameter, and often
encircle a twig. Larvae of the eastern tent caterpillar may be distinguished
from those of the forest tent caterpillar, Malacosoma disstria,
by the coloration pattern of the back. Forest tent caterpillars
have a row of diamond-shaped white spots alternated with small white
dots along its back. Forest tent caterpillars, contrary to their
name, do not build tents, feeding openly instead, often in large
groups or clusters.
tent caterpillar (left) and
forest tent caterpillar (right)
tent caterpillar eggs on twig
of the Eastern tent caterpillar
Eastern tent caterpillars spend the winter in the egg stage in
masses containing several hundred eggs. The eggs hatch in early
spring, about the time apple and cherry leaves unfold. After hatching,
the young caterpillars, sometimes from several egg masses, gather
in a fork in the branches where they construct a web-like tent.
The tents are used as shelter by the caterpillars when they are
not feeding on the leaves of nearby branches. Eastern tent caterpillars
feed from four to six weeks and then disperse to various locations
to spin cocoons and pupate. Cocoons may be found on fences, houses,
in weeds and ground debris, and on the trunks of infested trees.
When the adult moths emerge in mid-summer, egg masses are laid on
small twigs, sometimes on the stems of very small trees. Only one
generation occurs per year, and these eggs will not hatch until
the following spring.
- Prune out and destroy the egg clusters during winter months.
- Remove nests from trees by hand or with a stick.
- If nest removal is impractical, a spray containing Bt (Bacillus
thuringiensis) can be effective.
David Gadoury, David B. Wallace, and Richard A. Casagrande. Revised
Photos from the Ohio State University Extension.