The Rural Voice, 1999-10, Page 30Hidden danger
While pests like the Fall Web Worm may be unsightly, it's less obvious pests
you really have to worry about in your woodlot.
By Bonnie Gropp and Keith Roulston
Sometimes it's not the obvious
dangers you have to worry
about but the hidden ones.
Certainly it's that way this year in the
case of woodland pests.
The obvious pest this summer in
southwestern Ontario has been the
infestation of Fall Web Worm which
shrouded branches on many trees
with ugly webs. But though they
might not look pretty, they really
aren't going to hurt anything.
While its nests may seem to be
prevalent. they are not a significant
problem. according to Steve Bowers,
stewardship co-ordinator with the
Ministry of Natural Resources
Clinton office.
He explains that of the three most
commonly seen web spinning
caterpillars. the Fall Web Worm is
probably the least harmful due to its
nesting season. Though it does attach
itself to a variety of forest species
because it arrives near the end of the
growing season its impact is
minimal.
"The leaves will be gone soon
anyway," said Bowers, "and the
branches will leaf out because the
buds for next year have been formed
for a long time now."
If it seems that the nests are more
prolific this year, Bowers said that
populations do tend to fluctuate
though he hasn't noticed any great
increase from previous years.
"Often to control them, people
will chop down the branch, doing
more damage to the tree than the
insect," he said. Though some may
find it distasteful, Bowers prefers the
more hands-on approach. "If you're
concerned and can reach the nest
then pull it down."
If the tree has ornamental value
Bowers said spraying with an
insecticide might be an option.
However, the spray has to infiltrate
the web to be effective.
Should either method be
impractical, don't be concerned about
26 THE RURAL VOICE
Fall Web Worm is unsightly, but in the long run not dangerous to trees.
Other, less -visible insects pose a much worse danger.
leaving the nest where it is. "The Fall
Web Worm doesn't usually get to
any population level where they are a
real problem. Getting rid of them is
more often about esthetics."
By comparison the forest tent
caterpillar doesn't spin much of a
web at all, but it can be devastating
when its numbers get large enough.
In recent years there have been no
major infestations in western Ontario
but there was one bad period in
Bruce County about 20 years ago,
Bowers says.
The forest tent caterpillar builds
only a small, resting place in a tree.
Female moths lay
eggs in one batch
and the eggs hatch
together. The forest
tent caterpillars
head for a crotch of
a tree and spin a
web as a place to
rest while not
eating. Unlike most
caterpillars, tent
caterpillars eat
together. They all march off to feed,
focusing on defoliating one branch at
a time. Together they return to their
nest to rest. They continue this
pattern all day long. In large number
they can kill trees and whole forests.
There have been reports of gypsy
moth larvae in southern Huron
County, Bowers says.
Gypsy moths have become one of
the most wide -spread and devastating
woodland pest in North America.
They are known to feed on the
foliage of hundreds of species of
plants.
A native of Europe, Asia and
North Africa, the
gypsy moth was
introduced to the
United States in 1869
by a scientist in
Medford,
Massachusetts who
wanted to breed it
with other moths to
create a new strain of
silk -producing
caterpillars or "silk
The Asian long -horned beetle
has the potential to devastate
Ontario's maple forests.