Blue Ridge Country - September/October 2018 - 62

LEFT: A hemlock
infested with HWA
is often under a
death sentence-a
real tragedy to
the Blue Ridge
Mountains and its
ecosystem.
BELOW LEFT:
Matt Cook drilling
holes into the
cambium layer
of a hemlock in
preparation of
injecting it with a
synthetic nicotine
compound to fight
against the HWA.

contains a healthy colony of HWA and
the woolly nurseries within are vibrant
and alive, whereas the branches where
the beetle has become established show
"dried disturbed wool," proof that the invasive adelgids have expired.
After leaving Kentland Farm, we drive to
Tech's insectary where the L. nigrinus are
being raised along with another predatory beetle, the close relative L. osakensis
from Japan. Of course, before this beetle
species could be released, it had to go
through the same rigorous vetting process
that L. nigrinus did in order to make sure
that no native species would be harmed.
Jubb next shows me the bottles where
the adult females lay their eggs, and, also,
the nursery containers where the young
live and eventually drop into an attached
bottle below so that the offspring can
spend the summer in soil. One can't help
but be impressed by what Virginia Tech
has devised in its battle against the HWA.
"The hemlock is a keystone species in
a climax forest," says McAvoy. "The tree
supports a suite of species from native
brook trout to salamanders to songbirds
such as the blackburnian warbler and
blue-headed vireo. It's imperative that we
do everything we can to save it."
Earlier, Scott Salom, professor of ento-

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mology at Tech, had told me that to save
our region's hemlocks a three-prong approach is needed: biological (predatory
beetles), chemical, and silvicultural. So
several weeks later, I head for the New River Gorge National River in Fayette County,
West Virginia, where National Park Service
biologist John Perez and many others labor to stop the advance of the HWA. Perez
tells me that so far the NPS has used the
Imidacloprid insecticide to treat an incredible 17,982 trees with about 25 percent of
those being trees that received additional
treatments. Trees need to be retreated periodically, especially if an infestation occurs.
"At the New River, Gauley River, and
Bluestone River Gorges, hemlocks are often a major component of the few remaining old-growth forests in the parks, with
some trees approaching 400 years old," he
says. "Hemlocks are known to harbor two
species of birds dependent on hemlock
forests: the Acadian flycatcher and blackthroated green warbler.
"The dense shade provided by hemlocks helps maintain the micro-climates
of globally rare cold-cove forests. Hemlock
forested riparian zones help maintain the
cool mountain streams so important to
native brook trout populations."
Interestingly, this insecticide is a neonicotinoid, which is based on the natural insecticide nicotine found in tobacco
plants. So the same substance which can
cause such damage to human health can,
in its synthetic form, be extremely toxic
to the HWA. Perez says the insecticide is
released into the soil and can be effective
in controlling the adelgids for up to seven
years. The cost to treat a 12-inch diameter
tree is about $24.
Since the mid-2000s, the NPS has also
been deploying L. nigrinus as a biological
control against the HWA.
"Our monitoring of this predatory beetle and its effects on maintaining healthy
hemlocks is encouraging," continues
Perez. "We continue to release them into
the park. We are hopeful that biological
controls can provide a long-term cure, but
they are not available commercially."
The biologist emphasizes that the NPS
is very concerned about the use of insecticides in riparian zones and has a $250,000
research project with West Virginia University to study the effects of insecticides
on soil macroinvertebrates, salamanders,

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Blue Ridge Country - September/October 2018

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