Originally
reported on
the South
Shore and
Cape Cod,
the new
insect
outbreak was
thought to
be an
infestation
of native
fall
cankerworms,
which were
also in the
area. These
usually
crash from
natural
causes after
about three
years, so
specialists
didn't think
there was a
problem.
But the
South Shore
defoliation
has
continued
and spread
for at least
a decade
now.
Horticulturalist
Deborah C.
Swanson of
the Plymouth
County
Cooperative
Extension/UMass
Extension,
raised the
alarm (and
kept raising
it) and in
2003, and
scientists
at the
University
of
Connecticut
and Cornell
finally
identified
the pest as
a new
arrival from
Europe,
Operophtera
brumata.
''This
was a tricky
little
critter that
snuck in
under radar
because it
shares many
of the same
hosts as the
cankerworm
caterpillar
and looks
very similar
to it," said
Childs. ''We
didn't
notice it
until
Deborah
started
notifying us
seven or
eight years
ago and the
first sample
she sent
were fall
cankerworms.
There were a
couple of
winter moth
caterpillars
in the
second
sample, but
I thought
maybe they
were just
spring
cankerworms.
I asked for
a third
sample in
2003, and we
sent that to
Dave Wagner
in
Connecticut,"
who first
identified
it as winter
moth.
Meanwhile,
the new moth
multiplied
because it
has no
natural
enemies
here. And
even though
the females
are
flightless,
it managed
to spread.
''We know
it's in the
coastal
towns from
Gloucester
to Boston,
in and
around
Boston out
as far as
Newton-Wellesley,
and pretty
much
throughout
southeastern
Massachusetts,
and most of
the Cape out
as far as
Eastham.
There's
going to be
more
research
this year to
locate it,"
said Childs.
Now the
numbers at
the center
of the
outbreak are
astounding.
''We've got
some crazy,
incredible
densities,"
said the
Brenda
Whited of
the UMass-Amherst
survey team.
Individual
banded
maples and
oaks in
already
hard-hit
Hanson and
West
Bridgewater
last winter
yielded up
to 1,600
females
laying eggs
on each tree
monitored.
Since winter
moths can
lay 150
eggs, that
adds up to
almost a
quarter of a
million
caterpillars
this spring
per tree.
Many of
these
inchworms
may starve
to death,
especially
if they
hatch before
the tree
buds swell,
and numbers
won't be
that large
inside Route
128,
as
the moths
just reached
here about
three years
ago. ''But
it's going
to get worse
for the next
five years,
at least,"
said Joseph
Elkinton,
forest
entomologist
and
ecologist at
UMass-Amherst.
Then, if
all goes
according to
plan, a
counter
measure will
start
kicking in.
Elkinton
collected a
predator of
the winter
moth called
Cyzenis
albicans,
in Nova
Scotia,
where they
were
released to
control a
winter moth
outbreak
there 50
years ago.
He is now
raising
these
caterpillar-killing
flies in the
quarantine
facility at
the USDA lab
Otis Air
National
Guard Base
in Falmouth.
''This is
important
because we
need to make
sure that
only Cyzenis
is released
and not some
other
organism
brought in
accidentally
with Cyzenis,
which is
very
specific to
winter
moths,"
Elkinton
added.
But the
moths have a
big head
start. ''It
took five
years for
them to
multiply
enough to
catch up
with the
winter moth
population
when they
were
released in
Nova
Scotia,"
Elkinton
said. After
that the
winter moth
population
declined
dramatically
there over a
couple of
years, and
has been
kept at a
low level
ever since.
Until
then,
however,
you're on
your own,
and trees
that have
been
defoliated
for several
years are
very
unhappy.
They face
decline and
even death
without
extra help.
(Canadian
research
found that
many trees
die after
four
consecutive
years of
complete
defoliation,
though this
will vary
with the
tree
condition
and
species.)
The tiny
green
inchworms
start with
oaks,
maples,
fruit trees,
ash,
rose-of-sharon
and
blueberry
bushes, but
almost any
leaves or
flowers are
fair game
after that.
One way to
tell if
you're going
to be hit
hard is to
check your
tree trunks
for the tiny
orange eggs
the moths
randomly
scatter in
bark
crevices.
Just before
they hatch,
the eggs
turn bright
red.
The
inchworms
usually
hatch around
April 20 and
immediately
weasel their
way inside
swelling
leaf buds,
where they
cannot be
reached by
sprays. The
leaves open
in tatters.
After that,
the
caterpillars
are ''free
feeders";
they spread
by swinging
tree to tree
like Tarzans
on their own
silken ropes
when looking
for a new
food source.
In the
past, the
state took
the ''atom
bomb"
approach to
caterpillar
outbreaks
with massive
and largely
ineffective
spraying of
chemicals
such as lead
arsenate and
DDT. Now
state
specialists
have learned
that
introducing
diseases and
predatory
insects that
kill only
that pest is
much safer,
and works
better, too.
A fungus
from Japan
called
Entomophaga
maimaiga
has all but
finished the
gypsy moth
as a serious
pest since
1989, though
it can recur
when springs
are dry
enough to
inhibit the
fungus,
which needs
wet
conditions
to thrive.
There are
outbreaks of
other
caterpillar
species as
well, for
even the
natives are
restless.
For some
unknown
reason, when
one type of
caterpillar
overpopulates,
several
other kinds
often follow
suit.
Perhaps the
weather
conditions
suit them
all. Or the
birds and
other
predators
have been
just too
busy keeping
up with
winter moths
to get to
them. Or
perhaps when
there were
more gypsy
moths
around, they
spread their
diseases and
pests to the
other
caterpillars,
Childs
speculated.
Winter
moth
caterpillars
are active
for only
about three
or four
weeks.
Around May
20, they
will dangle
down to the
ground on
skeins of
silk and
burrow into
the top
layer of
soil, where
they will
become
dormant
pupae until
emerging as
adult moths
between
Thanksgiving
and New
Year's for
their
nighttime
mating
ritual. They
don't eat
anything
then. The
males just
flutter
around and
mate with
the
flightless
females, who
clamber up
trees, lay
eggs, and
die. Then
next April
those eggs
will hatch .
. . and on
and on it
goes. 