Defoliators
> Cankerworm
Pest: Fall Cankerworm (Alsophila pometaria (Harris));
Spring Cankerworm (Paleacrita vernata (Peck)
Order: Lepidoptera
Family: Geometridae
Description:
Cankerworms are caterpillars when immature and later develop into
moths as adults. As immatures, they have elongate, cylindrical bodies
with a well developed head capsule. In addition, they also have
3 pairs of thoracic legs. Further back on the body, they also have
2-3 pairs of abdominal legs known as prolegs. The Spring Cankerworm
has 2 pairs while the Fall Cankerworm has 3 pairs.
The adult male cankerworms (of both species) are rather dull-colored,
small moths while the females are wingless. They both get their
names from the times of the year in which they are active as adults;
the spring cankerworm adults are active in February into March while
the fall cankerworm adults are active in late November into early
December. They mate and lay eggs during these times.
The Problem:
Both the Spring and Fall cankerworm eggs hatch about the same time
in the spring. In Massachusetts, hatch occurs about mid-May. Caterpillars
of both species may be found feeding together in mixed populations
on the same host plant. The larvae feed on the foliage of many deciduous
trees including: oaks, cherry, elm, apple, maples, and others. Their
feeding initially causes the foliage to become very tattered in
appearance but later they may completely defoliate the entire host
plant. The immature stage (caterpillar stage) lasts until about
the end of June in Massachusetts.
For the past 2 years, many of the maple trees
(in particular) were severely injured by these caterpillars in the
Plymouth County area of Massachusetts. Another peak population year
for 2001 is expected.
Adult male moths of the Fall Cankerworm sometimes
become nuisance pests in late November and into December because
they are very attracted to night-time holiday lighting.
The Solutions:
Bacillus thuringiensis, commonly known as B.t., is sold under
many different trade names and is quite effective against the younger
caterpillars. This product is relatively "safe" when compared
to chemicals.
Cankerworm populations tend to build up into large, damaging
numbers over the course of several years and then almost entirely
disappear due to natural causes in the environment.
Images:
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A female cankerworm adult. Note that this is a wingless moth.
Close up of an adult female cankerworm moth (R. Childs)
Three fall cankerworm larvae. Note the 3 pairs of prolegs.
A spring cankerworm caterpillar. Note the 2 pairs of prolegs.
An adult wingless female spring cankerworm producing an egg
mass on the trunk of a tree. (R. Childs)
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Defoliators
index:
Armyworm
Asiatic Garden Beetle 
Bagworm
Cankerworms
2006
Caterpillar Update
Eastern Tent Caterpillar
Fall Webworm
Forest Tent Caterpillar
Gypsy Moth
Japanese Beetle
Larch Casebearer
Lily
Leaf Beetle -
Courtesy of URI Extension
Mimosa Webworm
Viburnum Leaf Beetle
Winter
Moth - ID & Management
UPDATED! Winter
Moth Overview
Winter
Moth Project - Biological Control in MA
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