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Combined Forest Fest
Home and Garden Bulletin
Defoliators of the
Major Hardwood Defoliators
of the Eastern United States
Robert L. Talerico'
In 1974 the U.S. Department of
Agriculture initiated the Combined
Forest Pest Research and
Development Program, an
interagency effort that
concentrated on the Douglas-fir
tussock moth in the West, on the
southern pine beetle in the South,
and on the gypsy moth in the
Northeast. The work reported in
this publication was funded in
whole or in part by the program.
This manual is one in a series on
the gypsy moth.
A variety of leaf-eating insects
periodically defoliates hardwood
trees in forests, on recreation sites,
and in residential areas in the
Eastern United States. An
occasional defoliation during the life
of a forest stand probably has little
effect on the overall growth of the
stand, but several years of severe or
varying levels of defoliation can
have negative impacts on the forest
community: Increased susceptibility
to other insects and diseases,
reduced foliage, and altered wildlife
In recreation areas, the unsightliness
of defoliated trees can result in
decreased visitor use and revenue.
A homeowner with a wooded lot
plagued with defoliating caterpillars
may incur the expense of spraying
and possibly the cost of tree
removal if mortality occurs.
'Research entomologist. Forest Insect &
Disease Laboratory. Hamden, Conn.
The insects discussed here complete
one generation each year. The adult
moths lay eggs, and in the spring
these eggs hatch into caterpillars, or
larvae, the most familiar life stage. It
is the larvae that eat the leaves of
the trees. After 4 to 6 weeks of
feeding, larvae spin cocoons and
enter a resting (pupal) stage. In
about 2 weeks moths emerge, mate,
and begin the life cycle once again.
Caterpillars feed on leaves in
different ways. A "free feeder" will
eat most of the leaf material (fig. 1).
Figure 1.-Leaves fed upon by
Figure 2.-Leaves tied or matted
together by insects for food and
Figure 3.-A leaf roll formed by an
insect for food and shelter.
Some larvae, called leaftiers,
construct feeding shelters by tying
several leaves together (fig. 2). The
caterpillar lives and feeds within this
mat of leaves, adding more leaves
for food as needed or moving to
other leaves. Other larvae are leaf
rollers, which make a feeding shelter
by rolling up the edge of a leaf and
live and feed within this roll (fig. 3).
Another roll is constructed when the
food supply is exhausted or the roll
becomes unsuitable for food or
Some common names of these
insects are derived from their
peculiar method of movement-
measuring worms, inchworms,
loopers, spanworms, and
cankerworms. The movement is
produced as the larva brings its hind
legs up to the forelegs, forming a
loop with the body, and then
extends the forelegs forward.
A behavioral trait shared by the
loopers, tiers, and rollers is the
reaction of the larvae when they are
disturbed. The slightest jarring of
the branch or leaf they are on
causes larvae to fall or descend on
silken threads to other branches or
leaves, where feeding continues.
To help landowners and others to
identify these defoliating pests, this
booklet describes eight insects and
details their life stages. For positive
identification of these insects and
control recommendations, consult
your county agricultural agent, State
experiment station, or the U.S.
Department of Agriculture.
Ennomos subsignarius (Hiibner)
The elm spanworm is found in most
areas of the Eastern United States
and adjacent Canada. The
caterpillars feed on elm, ash,
hickory, and oak but rarely on
yellow-poplar. In the past this insect
has been a serious defoliator of
shade trees in large cities; more
recently, severe and widespread
outbreaks have occurred in forested
areas of the southern Appalachians
Spanworm eggs are laid in irregular,
single-layered, compact masses on
the underside of twigs or large
branches or on tree trunks. They are
bright yellow green when first laid
in the summer but darken to a dull
olive or gray in winter (fig. 4).
Figure 4.-Elm spanworm egg
Figure 5.-Elm spanworm larva.
Figure 6.-Elm spanworm pupa
and cast larval skin.
Figure 7.-Adult elm spanworms.
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In the spring, egg hatch occurs
about the time tree buds begin to
unfold. The manner and location of
feeding change as the larvae grow.
Young larvae feed on the underside
of leaves, causing a shothole effect.
As they mature, larvae eat all leaf
material between the major veins.
Full-grown larvae are about 50 mm
(2 in) long and are usually dull, slate
black with a rust-colored head (fig.
5). Color variation occurs in mature
larvae in response to increased
population levels. Mature larvae
pupate in loosely constructed silken
cocoons between partially
consumed leaves, on branch tips, in
bark crevices, or on understory
vegetation (fig. 6).
The adult moth, which emerges in
July, is pure white and has a
wingspan of 30 to 37 mm (1 to 1.5
in) (fig. 7).
Alsophila pometaria (Harris) and
Paleacrita vernata (Peck)
Cankerworms have been
documented as native North
American tree pests since colonial
days. Spring and fall cankerworms
are similar in distribution,
appearance, and the damage caused.
The fall cankerworm lays its eggs in
November and early December, and
the spring cankerworm in late
February and March. The female
moths of both are wingless.
Cankerworm infestations have been
reported in the Canadian Maritimes,
southern Canada, and the Eastern,
Midwestern, and Western United
States. The spring cankerworm
tends to range further to the
Southwest and West. Both have a
wide range of hosts that include
deciduous forest, shade, and fruit
trees. Apple and elm seem to be
Figure 8.-Egg mass of fall
cankerworm. Old eggs can be
distinguished from new eggs by the
presence of holes in tops of eggs.
preferred, but many oaks, maples,
hickories, ashes, and beech are also
The fall cankerworm lays about 100
eggs in an aligned, compact, single-
layered, reddish-brown mass, which
becomes gray as it weathers (fig. 8).
The masses can be found directly
on small branches, at the juncture of
a branch and a tree trunk, and
directly on tree trunks. Occasionally
a single egg will be laid. It is
possible to distinguish old eggs from
new by the absence of a covering on
The eggs of both species of
cankerworms hatch in the spring,
and it is not unusual to find them
feeding together on expanding buds
and foliage. Larval feeding lasts 4 to
6 weeks. Feeding by young larvae
produces a shothole appearance on
the leaves. Older larvae consume all
leaf material but the major veins.
Full-grown fall cankerworm larvae
vary from light to dark green and
are about 25 mm (1 in) long (fig. 9).
Mature spring cankerworm larvae
are 18 to 30 mm (0.8 to 1.3 in) long
and vary considerably in color,
ranging from reddish to yellowish
brown, yellowish green, or black.
The head is light and mottled with a
yellowish stripe along each side of
the body, and a broad, greenish-
yellow stripe runs the length of the
undersurface of the body.
Some older fall cankerworm larvae
have a dark stripe running
lengthwise down the back; light-
green larvae have white lengthwise
lines. Larvae of the fall cankerworm
have three pairs of hind legs or
claspers. One pair is smaller,
sometimes indistinct, and in front of
the two obvious hind legs (fig. 10).
The spring cankerworm lacks this
additional pair of hind legs.
When the larvae finish feeding in
early July and are ready to pupate,
they crawl or spin down on silken
threads to the ground and prepare
cocoons in the soil. Fall
cankerworm adults emerge in
November and early December,
frequently after some freezing
weather; spring cankerworm adults
emerge in late February and March.
Fall cankerworm male moths are
brownish gray with a wingspread of
25 to 35 mm (1 to 1.4 in) (fig. 11);
Figure 9.-Fall cankerworm larva.
Figure 10.-Side view of fall
cankerworm larvae showing the
three pairs of hind legs.
Figure I11.-Adult male fall
Lymantria dispar (Linnaeus)
the wingless females are about 12
mm (0.5 in) long (fig. 12).
Spring cankerworm adults are
similar to the fall cankerworm. Male
moths have a wingspan of 21 to 30
mm (1.0 to 1.3 in). The forewings
are silky brownish gray, crossed by
three jagged dark lines. The
hindwings are pale ashy gray with a
darkened central spot. Females are
wingless, generally white, with
brown or black hairs, with a dark
stripe down the back. Both have
two transverse rows of reddish
spines on the back. These are more
prominent in the female and give the
back a reddish cast.
Figure 12.-Female adult fall
cankerworm. Note the lack of
Gypsy moth egg masses were
brought to the Boston area in 1869
from France for experimental
crossbreeding with the silkworm.
Unfortunately some of the larvae
escaped and became established on
the local vegetation. The insect has
now spread throughout New
England, the Mid-Atlantic States,
southeastern Quebec, and central
Michigan. Scattered infestations
have been reported along the east
coast to Florida and as far west as
California. Hosts include most
hardwoods and any conifer that
might be mixed in with the more
favored hosts of oak, gray birch,
and poplar. Yellow-poplar and ash
are usually avoided, but in outbreak
situations the larvae will eat just
In late summer, eggs are deposited
in masses (fig. 13) containing 75 to
800 eggs that are covered with buff
to light-brown hairs from the
female's abdomen (fig. 14). These
hairs insulate the eggs from low
winter temperatures. Most egg
masses are deposited on the trunks
and limbs of trees, but they can also
be found under stones, inside hollow
trees and stumps, on leaves, and on
various manmade objects. Eggs
hatch in late April or early May,
usually about the time the oak
leaves are expanding.
Newly hatched larvae move from
the egg masses toward the top of the
tree. When disturbed, larvae will
spin down on silken threads; this
behavorial trait, along with a small
body size and long body hairs,
makes this stage very susceptible to
airborne dispersal by the wind. This
type of dispersal can spread an
infestation up to 1.6 km (1 mile) in
flat terrain or more than 7 km (4.4
miles) in hilly topography.
A full-grown larva is 40 to 60 mm
(1.5 to 2.4 in) long. The head has
patches of yellow markings; the
body is a dusty or sooty black with
tufts of hair on each body segment.
On the back is a double row of five
pairs of dark blue spots, followed by
a double row of six pairs of brick-
red spots (fig. 15).
Young larvae chew small holes in
leaves. Older larvae feed on leaf
edges, consuming entire leaves
except for the larger veins and the
middle rib. Feeding by the large
larvae occurs mostly at night.
During the day, the larvae
congregate in sheltered locations. If
trees are completely defoliated
before the larval stage is finished,
larvae leave the bare trees to search
for another food source. This short
distance movement can become a
nuisance in wooded residential
areas. The homeowner becomes
acutely aware of the wandering
larvae, which fall into swimming
pools and climb all over lawn
furniture, patios, and shrubbery.
Figure 13.-Gypsy moth egg mass.
Figure 14.--Closeup of eggs of the
Larval feeding is completed by mid-
June or early July and is followed
by pupation, which lasts about 2
weeks. The pupa is dark reddish
brown with a sprinkling of reddish
hairs. Adults emerge and mate from
mid-July through August. Egg laying
occurs at this time.
The male moth has a wingspan of
about 37 mm (1.4 in) and is dark
brown with black bands across the
forewings (fig. 16). The female is
white with variable black bands
across the forewings (fig. 16) and
her abdomen is covered with buff or
light-brown hairs. She is larger, with
a wingspan of about 50 mm (2 in),
but rarely flies.
Figure 15.-Gypsy moth larva.
Figure 16.-Adult male (brown)
and female gypsy moths.
Phigalia titea Cramer
The half-wing geometer is frequently
found in association with
cankerworms, elm spanworm, and
linden looper. Its distribution is
believed to be in the eastern half of
North America (southern Canada
and various States along the
Atlantic coast). Hosts of this
geometer are most hardwood trees,
including various oaks, hickories,
and red maple.
Eggs are laid in early spring in
protected locations on branches, on
tree trunks, and under loose pieces
of bark (fig. 17). The eggs hatch in
April, and the larvae feed until early
June. At first the larvae feed only
Figure 17.-Half-wing geometer
on the leaf surface, but as they grow
and develop, they feed on all leaf
tissue between the major veins. A
full-grown larva is about 37 mm (1.5
in) long. The head and body are
cream colored with many
lengthwise black, wavy lines that
make the larva appear black (fig.
18). Usually by the first week in
June larval feeding slows, and the
larvae crawl or spin down on silken
threads to the ground and begin to
pupate in the soil.
The adult male moth is gray with
black markings and has a wingspan
of 37 mm (1.5 in) (fig. 19). The
female is ash gray, resembling the
cankerworm, but with very small (3
mm, 0.13 in), functionless wings.
The adults emerge from late March
to mid-April, even in adverse
Figure 18.-Half-wing geometer
Figure 19.-Adult male of the half-
Forest Tent Caterpillar
Malacosoma disstria (Hiibner)
Figure 20.-Forest tent caterpillar
Figure 21.-Forest tent caterpillar
The forest tent caterpillar is a native
insect that occurs throughout most
of the United States and Canada.
This caterpillar feeds on a wide
variety of hardwoods. In the North
and West, trembling aspen is
preferred. Forest, orchard, and
ornamental trees are also
acceptable, and several extensive
outbreaks of the insect have
occurred in the past.
Eggs are laid in masses containing
100 to 350 eggs. The mass is a
cylindrical band, ringlike in shape
and 25 to 37 mm (1 to 1.5 in) wide,
that encircles the twig (fig. 20). The
ends of the mass are square, and the
whole mass is coated with a dark-
colored, gluelike substance. Winter
is spent in the egg stage, and
hatching occurs in the spring about
the time the tree buds begin to
Figure 22.-Pupal case of forest
Figure 23.-Adult male (left) and
female forest tent caterpillars and
an egg mass.
Erranis tiliaria (Harris)
Young larvae feed on the expanding
buds; the older ones eat the foliage.
Young larvae from one egg mass
feed together as a group on a leaf or
leaf cluster. As the larvae grow and
mature, the group breaks up and
each larva feeds alone on the
foliage. Full-grown larvae are about
50 mm (2 in) long with a light bluish-
black head and a few scattered
white hairs. The back of the body is
marked lengthwise with a row of
spots. The remainder of the body is
various shades of gray (fig. 21).
Larvae lay down strands of silk as
they move about. They also form
silk mats on the trunks and
branches on which they collect in
groups to rest between feedings.
Contrary to the common name, a
tent is not constructed by the larvae.
As they approach maturity, they
wander about individually in search
of food or places to pupate.
Pupation occurs in pale-yellow
cocoons about 25 mm (1 in) long
that are spun in folded leaves, bark
crevices, and other protected sites
(fig. 22). Depending on the
geographic location, the appearance
of adults occurs from late May in
the South to early July in the North.
The stout-bodied, light buff-brown
adults have a wingspread of 25 to 37
mm (1 to 1.5 in) (fig. 23).
This looper is a native defoliator
that may be found in southeastern
Canada and throughout the Eastern
United States. It defoliates forest,
shade, and fruit trees, such as
basswood, elm, hickory, maple, oak,
birch, and apple, and is often found
Eggs are laid singly or in small
groups, usually in bark crevices.
Winter is spent in the egg stage.
Hatching occurs in April and May
as the leaf buds are expanding.
Larvae feed on the foliage until July,
then they crawl to the ground and
burrow 25 mm (1 in) or more into
the soil to pupate. The full-grown
larva is about 37 mm (1.5 in) long,
bright yellow, with 10 black wavy
lines running lengthwise down the
back. The head is rusty brown (fig.
Figure 24.-Linden looper larva.
Figure 25.-Adult male (left) and
female linden looper.
Male moths have a wingspan of
about 42 mm (1.7 in). The forewings
are buff colored and marked with
two transverse wavy brown bands
and a sprinkling of brown dots. The
hind wings are lighter and without
distinctive markings (fig. 25). The
female is wingless, about 12 mm (0.7
in) long and is colored from light
gray to brown, with two rows of
black dots on her back (fig. 25).
Croesia semipurpurana (Kearfott)
The tiers are a very important group
of defoliators. It is not unusual for
tiers, rollers, cankerworms, and
loopers to feed on the same trees.
The oak leaftier has been collected
in many States, from New York
south to Texas, fyom Massachusetts
west to Minnesota, and from
adjacent areas in southern Canada.
Tiers appear to have a preference
for red, scarlet, black, and pin oaks.
Periodically the tier has been a
serious defoliator of forested areas
in Pennsylvania, and tree mortality
has been attributed to tiers following
a number of years of sustained
In June, eggs are laid singly on twigs
with rough bark, where they
overwinter. After hatching the
following April, the young larvae
enter unopened buds and feed on
the developing leaves. Large
populations can destroy nearly all
the buds on a tree. Surviving buds
produce leaves riddled with holes.
Major defoliation results from the
feeding of older larvae, which feed
more openly but from within their
protected webbing and shelter. The
full-grown larva is about 12 mm (0.5
in) long and dirty white to light
green (fig. 26). It has a pale brown
head and black to brown front legs.
Figure 26.-Oak leaftier larva.
Note black bar on lower side of
head or cheek area.
Oak Leaf Roller
Archips semiferanus (Walker)
A black bar on the lower side of the
head or cheek area is a distinctive
character for identification. When
larvae mature in mid-May, they spin
down on silken threads to the
ground and pupate in the litter
beneath the tree. Adults emerge and
mate from late May through June.
The oak leaftier adult moth is small,
with a 12 mm (0.5 in) wingspan. At
rest the wings appear bell shaped. A
great deal of variation exists in the
color pattern of the moth's forewing,
which may vary from almost
uniform yellow to yellow with dark
brown markings (fig. 27).
Figure 27.-Oak leaftier adult
The rollers are a large group of
insects that are still being identified,
described, and studied by experts.
This roller is periodically a serious
defoliator of native oaks in the
eastern half of the United States and
adjacent Canada. Although all oaks
are fed on, defoliation is usually
most severe along ridge tops where
white and chestnut oak frequently
occur. Occasional feeding has been
reported on witchhazel and apple.
Severe infestations have occurred
recently in Pennsylvania.
During July, masses of 40 to 50 eggs
are laid at the base of large branches
and rough bark patches on both tree
trunks and limbs (fig. 28). The
masses are covered with hairs from
the female's body. These eggs begin
hatching in late April. The larvae
either fold or roll individual leaves
together, forming an enclosure in
which to rest and feed or from
which they move out to feed. Full-
grown larvae are about 29 mm (1.2
in) long. The head is black, and the
body can be various shades of green
Pupation occurs in silken cocoons
within the roll or in bark crevices
(fig. 30). The moths emerge in late
June and July. At rest, the wings of
the adult appear bell shaped. The
forewing varies in color pattern but
ranges from creamy brown at the
base to gray at the tip. Midway
down the wing is a distinct dark
brown or gray oblique band across
the wing. The wingspan is about 18
to 22 mm (0.7 to 0.9 in) (fig. 31).
.Figure 28.--Oak leaf roller
Figure 29.--Oak leaf roller
.Figure 30.--Oak leaf roller
pupae on tree trunk.
Figure 31 ----Oak leaf roller
Key to Identifying Larvae
Key Refer to
No. Key No.
1. A. Larva feeds and lives
within a leaf roll or
B. Larva feeds freely,
does not construct
leaf roll or leaf mat
2. A. Head pale brown
except for a
longitudinal black bar
on the lower cheek
(side of head); region
Oak l iflici (fig. 26)
B. Head with irregular
black markings on
other areas besides
cheek; often most of
head dark brown to
darkened on top and
roller (fig. 29)
3. A. Larva hairy or with
tufts of hair on each
B. Larva with few body
hairs, almost bare
4. A. Larva dusty or sooty
black; on back, a
double row of 5 pairs
of dark blue spots
followed by a double
row of 6 pairs of
brick red spots
(Gypsy moth (fig. 15)
Key Refer to
No. Key No.
B. Larva dark blue
2 keyhole-shaped spots
Forest tent caterpillar
3 (fig. 21)
5. A. Larval body bright
yellow; back with 10
Linden looper (fig.
B. Larval body not
6. A. Larval body and head
cream colored with
black wavy lines
B. Larval body light to
7. A. Larva may have a
brown stripe on back
or white lengthwise
lines; three pairs of
4 hind legs, one pair
smaller and in front
5 of others
(figs. 9 and 10).
B. Larval body a dull
slate black, variable;
two pairs of hind
Photographs to illustrate the various
insects and their stages were
supplied by: D. C. Allen, State
University of New York, Syracuse,
N.Y.; A. T. Drooz, Forest Service,
Research Triangle Park, N.C.; S.
Jarrett, Forest Service, Delaware,
Ohio; E. E. Simons, Pennsylvania
Department of Environmental
Resources, Middletown, Pa.; and R.
T. Zerillo, Forest Service, Hamden,
Issued November 1978
Available from the Superintendent of
U.S. Government Printing Office
Washington, D.C. 20402
UNIVERSITY OF FLORIDA
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