10, 2006 08:01 PDT
If balsam woolly was more effective elsewhere than in the
the Black Mountains, then it must have been beyond devastating.
Entire mountaintops of fraser fir were wiped out in the Smokies
and Blacks. A few older trees have survived in both ranges, a
on Mount Guyot possible being the largest group, but those are
exception. Mount Mitchell (6684'), in the Blacks, currently
much better than Clingmans Dome (6643'), in the Smokies. I have
the greater regeneration on Mitchell attributed to a heavier
at the time the adelgid moved through, rather than differences
resistance. The only other fir population I have seen is the
southernmost one, near Richland Balsam on the Blue Ridge
have seen no old looking fir trees at that population, but it
have larger regrowth trees.
The generation of fraser fir that have grown up post adelgid are
relatively young with smooth bark, so they have not reached
susceptibility yet; the balsam woolly adelgid feeds primarily
cracks and fissures in the bark. I don't know if baseline data
to judge the susceptibility of the current generation.
I am far more optimistic for the future of fraser fir than I am
our hemlocks, because fraser fir can reproduce before being
balsam woolly adegid. Hence, they should be able to evolve
bark and earlier reproductive age and minimize the impact of
woolly adegid. If they can handle global warming, ozone
and acid deposition, they should be able to once again cover the
peaks of the southern Appalachians. Conversely, hemlock woolly
adelgid kills two inch tall seedlings. Natural resistance and
environmental protection also appear less with hemlocks, so
may have to have help to recover.
On 7/5/06, James Smith wrote:
There must certainly be examples of diseases that have
managed to wipe
out the host populations. Just because it's not terribly
in an implacable evolutionary way--doesn't mean that an
wouldn't capitalise on a host's weaknesses to completely
wipe them out.
I know almost nothing about the subject, but I would
assume that thing
like that have occurred over the course of the history
of life on Earth.
On the other hand, hasn't the balsam wooly adelgid shown
signs that it's
not as effective on the trees in the Smokies and Blacks?
newer generations of balsam trees coping with the
introduced pests? Or
is it merely because the adelgids prefer older trees? Or
adelgids die off after the initial onslaught when almost
all of our
balsam forests were destroyed?
If the balsam trees are, indeed, showing more resistance
to the balsam
wooly adelgid, perhaps this bodes well for the eastern
hemlock species. Perhaps after they are initially wiped
out, a newer
generation will be more likely to resist the pest.
Hasn't it been conjectured that a feline virus almost
wiped out the
cheetah? Haven't genetic tests shown that at some time
in the past the
breeding population of the entire species was reduced to
just a few
dozen individuals? If so, then that would be an example
of a disease
coming pretty darned close to completely wiping out a
Balsam woolly adelgid
10, 2006 18:12 PDT
How long have the adelgids been tearing through the Smokies?
I ask because when I look back upon some of my photos of the
in 2004 on a road trip there, in certain areas there seem to be
more dead trees in the woods than you'd think there should be...
straight, grey trunks of what I assume are evergreens... Could
the effects of the adelgid?
Balsam woolly adelgid
10, 2006 19:50 PDT
that was the balsam wooly adelgid. It devastated the balsam
Darned near wiped them out in some areas. To me, the most
sights were in the high elevation areas along the Blue Ridge
in the Great Smokies. Mount Mitchell, at one point, seemed to be
more than a mass of dead snags. Still lots of dead trees
there, but vigorous new growth of young trees, so it's not as
it was fourteen or fifteen years ago.
Balsam woolly adelgid
11, 2006 14:21 PDT
Balsam woolly adelgid did kill entire stands of trees decades
that now all that remains are stands of limbless snags. However,
you were just seeing an unusually large number of snags in an
that would still qualify as woods, you were probably looking at
red spruce. Spruce have been stressed by acid deposition and
factors over recent decades and many in the park have died,
on the Tennessee side.