As
you are aware the Gypsy Moth is
an invasive species which can put
into motion devastating consequences
to trees which are under stress
due to drought or other secondary
insects and diseases, both native
and invasive.
At
the beginning of an infestation,
an average of 1250 Egg Masses per
hectare (EM/ha) generally indicates
a population that will cause 40%
or more defoliation the following
growing season. Less than 40% defoliation
is not readily visible to the untrained
eye, and has minimal effect on tree
health. Once defoliation exceeds
40% to 50%, defoliation is readily
visible, and tree health can be
adversely affected. Although trees
usually refoliate if they lose more
than 50% of their foliage, this
is an additional stress on the trees,
and uses up their starch reserves
for future growth.
If
egg mass counts exceed 4000 EM/ha,
the population is healthy (low parasitism
and infection rates) and the egg
masses are large (i.e. quarter size
or larger, rather than dime size),
defoliation greater then 50% should
be expected. If the same healthy
populations exist, and there are
more than 10,000 EM/ha, 100% defoliation
of susceptible trees can be expected.
Areas
identifed on the map had an estimated
Egg Mass counts in excess of 10
000 EM/ha. The highest counts were
in the Harmony Rd. area north of
Nixon with 144,000 EM/ha.
Gypsy
Moth is a landscape issue. It does
not distinguish between property
lines, farms or urban lots. It is
imperative that all landowners make
informed decisions, taking into
account that in order for the control
of this insect to be effective,
ideally all affected lands need
to be sprayed. Those landowners
adjacent to individuals who do not
spray, in high infestations, will
see an impact as the insect seeks
out new food sources.
UPDATE
- JULY 3rd, 2008
Gypsy
moth is an invasive species and
heavy or repeated defoliation puts
at risk your trees health. Gypsy
Moth feeding is at its peak right
now. As the weather warms the larvae
move down from the top of the tree
to seek shade and a cooler space
until nightfall when they travel
back up the tree to feed.
Options
for control are limited at this
stage. Banding of the trees can
reduce the larvae if they are caught,
via sticky tape, or by manual removal
daily.
A
number of natural controls have
been noted and their impact will
only be fully assessed through fall
surveys in those areas in which
heavy defoliation was noted.
The
natural controls County staff has
documented can be one of three agents
•
nucleopolyhedrosis
virus ( NPV) a natural
occurring virus specific to gypsy
moth, from which the Gypchek research
product is derived;
•
Entomophaga
maimaiga an introduced fungus,
and;
•
Fly and wasp parasitoids native
and introduced.
Caterpillars
killed by NPV often remain attached
to the stem or branches of trees.
The bodies of dead caterpillars
are soft, filled with a brown liquid
and disintegrate rapidly. Usually,
they hang limply in an inverted
"V" position.
Caterpillars
killed by E. maimaiga
will also remain attached to tree
stems or branches. However, the
bodies tend to be stiff and straight,
and the legs extend stiffly from
the body. Some of the dead caterpillars
may have tiny white conidia attached
to the hairs on the body. The cadavers
may remain on the stem well into
the winter. E.
maimaiga infections are noted
as more common in years with rainy
spring weather than in years with
a dry spring thus the increase
we are documenting.
County
staff has been encouraging individual
landowners with single lots or a
manageable number of trees to burlap
band their trees so those larvae
that are infected spread the virus
to other larvae when they travel
down the tree to seek a cool shady
location, in which the burlap provides.
Landowners are advised not to remove
the infected lethargic larvae the
virus that has grown within these
larvae leaks from their bodies and
other larvae in turn become infected
spreading the virus.
It
should be noted NPV is seldom prevalent
until gypsy moth populations reach
very high levels. In contrast, E.
maimaiga may be found even
when gypsy moth populations are
low.
It
has been noted the parasitization
of gypsy moth by the introduced
tachinid fly (C. concinnata) is
occurring but such levels are
low. Literature indicates that control
through this agent is generally
low (less than 5%) during gypsy
moth outbreaks and is only found
in higher levels on a declining
population. It should be noted that
when tachinid fly populations are
high there has been documentation
that it will impact 180 species
of native Lepidoptera in North America
.
Landowners
over the next 10 days will begin
to see the pupation of the larvae
into moths. The female moths do
not fly only the males do. They
do not feed and only breed during
this life stage. It is recommended
that landowners use a pheromone
trap to disrupt the male moth during
this breeding phase. While effectiveness
in managing the overall population
is limited every male moth killed
through these means lowers the potential
that all female moths will have
their eggs fertilized.
Unfortunately
damage to trees in those areas forecasted
with high populations is severe
this year the late frost set into
motion a rapid defoliation for those
trees that re-flushed after the
frost damage when the insect was
in its early stage of development.
Those
areas treated are showing significant
results, with a few instances with
treated areas being impacted from
non-treated areas. County staff
have begun to document these areas
and have begun to document trees
which have not re-flushed to assess
the long-term impact, including
branch dieback or mortality. An
aerial survey will be undertaken
in the coming weeks in partnership
with the Ontario of Ministry of
Natural Resources.
OPTIONS
FOR CONTROL ON
INDIVIDUAL
LOTS AND SINGLE TREES
CLICK
HERE
Managing
your woodlot.
Each woodlot owner is entrusted
to manage their woodlot for future
generations. Decisions today will
not only impact the present owner
but neighbours, and future woodlot
owners.
Be
informed. Know the
pros and cons of managing for your
objectives, for your woodlot. Be
prepared to accept the results of
those decisions.
2008
Gypsy Moth Proposed Control Areas
-
map attached indicates potential
defoliation zones
CLICK
GYPSY MOTH for .pdf 
Information
and links regarding the biological
spray product
Btk
Bacillus
thuringiensis subspecies
kurstaki
