Grand vista south with Ron in tree #2
June 7th I and three others climbed some huge, old-growth
hemlocks in the Great Smoky Mountains National Park. The trees
120 to over 150' tall. We were hired to collect foliar samples
to assess the
concentrations of imidacloprid in the needles. Imidacloprid is a
insecticide (manufactured by BAYER) widely and successfully used
combating the hemlock woolly adelgid. Ten trees were treated on
Cataloochee, in November 2002 with a soil application of 75% WSP
concentration at the maximum dosage on the label (1.6 oz per
24" diameter at
4.5 feet). We had previously climbed these trees in the spring
of 2003 to
collect foliar samples, and some imidacloprid was detected. This
climb was to assess the recovery of the trees (my goal as an
to see if the chemical is still in the tree and in what
of the NPS goals). Very little is known about how to treat huge
Brian and Jason in tree #6 (left) and #7 (right) respectively.
Brian perched over the abyss.
Chris in tree 5.
Descending tree #1.
Overall, the climbers reported the trees to be essentially clean
with very little to no living insects found on the trees. What
was that some of the trees had a heavy crop of HWA this year but
dead and no new brood (May-June) was detected after the first
following winter (March- April). Distorted new growth was
evident on the
more vigorous portions of the trees. Heavy HWA infestations
a "droop" in the terminal leader of the branch, which
can lead to a
distorted twig after recovery (see photo).
Dead adelgids from spring 2005- no second brood!
Distorted but healthy re-growth.
Ron in tree #2.
All trees exhibited varying degrees of recovery with seemingly
fully green and growing next to gray, declining limbs a few
inches away. The
apparent delay in chemical activity and the light to moderate
the time of treatment may explain the patchy recovery.
heavily infested limbs would be more impacted than the light to
limbs. In general, the tops of the trees were much
vigorous than the lower limbs. However, some trees had
limbs with mid-canopy limbs devoid of new growth. If no buds
previous infestations the limbs will die as the older needles
Tree #8 gnarl detail stitched.
Lichen garden Tree #8 stitched.
Will in top of Tree #8 @ 140'.
Tree #6 and #7 stitch; Brian at base of #6.
#9 seems destined to die, as it had almost no new growth and was
differentiated from the non-treated trees. Tree # 10 however,
excellent shape and was green throughout the canopy. Typically,
trees surrounding the 10 treated trees were gray and declining
There were a few green trees visible here and there, suggesting
predator beetle release may be having an impact.
Tree #10 green and happy- imidacloprid works!
Ron in tree #10 full view.
Will and Ron in canopy; tree #8 (Will-left) tree # 10 (Ron-right), northwest view.
Tree 10 composite 2003.
Just two years of HWA made a huge impact. Just look at the
photos taken in
2003 and compare them to 2005. In 2003, the trees were all
green. In 2005
the treated trees were easy to pick out as they were simply--
Essentially no new growth was seen on neighboring trees, and
some trees were
already dead, but maybe not entirely due to HWA. In addition to
entire tops of neighboring hemlocks were infested with HWA for
lengths of 10
feet or more covering even the trunk to 3 inches in diameter.
South vista 2003
Jim Branch north vista 2003.
Grand vista north
Gray ghost 2005.
I have yet to hear the results of the study, but I know that
works. I use it almost daily against HWA and have had excellent,
delayed results. Some trees I treated in 2001 are still free of
only one soil treatment. It seems the Jim Branch trees may need
dose, but we will know for sure soon. Other studies indicate
that a very
small concentration of imidacloprid can prevent HWA
recovery seems slow on these huge trees.