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It's worthwhile questioning the ability of spring migrants to spread
insects, such as the hemlock woolly adelgid (HWA). Invariably it's us
humans who are the direct/indirect original vectors of introduction (and
this is the case with HWA as well). I am interested to learn more about
the spring migration routes of species such as Bay-breasted and
Blackburnian warblers, as well as Blue headed vireo, and other high
canopy gleaners of insects in hemlock stands.
I understand that HWA has been migrating more or less steadily toward
northern Maine over the past decades, slowed somewhat by some of the
colder winters. Everything points to it reaching there eventually.
Since the pest consists of "all females", HWA needs only one new
individual to start a whole new population. (We can only hope this could
lead to part of its vulnerability.)
HWA needs to actually land on hemlock. I am not certain that NB has a
lot of hemlock at the border, but it likely features much less than it
once did, given the species sensitivity to fire, land clearance and
clearcuts. (My research in eastern NB indicated a precipitous decline
in expansive hemlock-dominated stands beginning in the early 1800s.)
There may be much less hemlock to become infested with HWA in NB than in
southwestern NS where some impressive hemlock stands remain. Other
plausible theories for HWA dispersal vectors to NS were from high wind
events and nursery stock. Birds seemed more likely to me, especially
given the extremely small size of HWA and its ability to stick fast to
feathers.
It's heart wrenching to watch.
Donna Crossland
On 2018-06-15 8:07 AM, John Kearney wrote:
>
> Hi David and all,
>
> That’s a very good question. I’ve heard the same reason given for why
> we have the Hemlock Woolley Adelgid in Nova Scotia but not in northern
> Maine and New Brunswick. I’m not aware of any evidence indicating that
> more spring migrants fly to Nova Scotia than Maine or New Brunswick.
>
> John
>
> *From:*naturens-owner@chebucto.ns.ca <naturens-owner@chebucto.ns.ca>
> *On Behalf Of *David
> *Sent:* Thursday, June 14, 2018 17:10
> *To:* naturens@chebucto.ns.ca
> *Subject:* [NatureNS] Lyme disease
>
> Dear All,
>
> In the July issue of Maclean's (p.17) are interesting data on Lyme
> disease incidence in Canada. The much higher incidence in NS, 21.5
> times as high as the average incidence in the other nine provinces, is
> attributed to "climate and the large number of migratory birds
> carrying ticks from the US."
>
> I don't follow why NS would be hit the hardest.
>
> Yt, DW
>
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<p>It's worthwhile questioning the ability of spring migrants to
spread insects, such as the hemlock woolly adelgid (HWA).
Invariably it's us humans who are the direct/indirect original
vectors of introduction (and this is the case with HWA as well).
I am interested to learn more about the spring migration routes of
species such as Bay-breasted and Blackburnian warblers, as well as
Blue headed vireo, and other high canopy gleaners of insects in
hemlock stands. <br>
</p>
<p>I understand that HWA has been migrating more or less steadily
toward northern Maine over the past decades, slowed somewhat by
some of the colder winters. Everything points to it reaching
there eventually. Since the pest consists of "all females", HWA
needs only one new individual to start a whole new population.
(We can only hope this could lead to part of its vulnerability.)
<br>
</p>
<p>HWA needs to actually land on hemlock. I am not certain that NB
has a lot of hemlock at the border, but it likely features much
less than it once did, given the species sensitivity to fire, land
clearance and clearcuts. (My research in eastern NB indicated a
precipitous decline in expansive hemlock-dominated stands
beginning in the early 1800s.) There may be much less hemlock to
become infested with HWA in NB than in southwestern NS where some
impressive hemlock stands remain. Other plausible theories for
HWA dispersal vectors to NS were from high wind events and nursery
stock. Birds seemed more likely to me, especially given the
extremely small size of HWA and its ability to stick fast to
feathers.</p>
<p>It's heart wrenching to watch.<br>
</p>
<p>Donna Crossland<br>
</p>
<br>
<div class="moz-cite-prefix">On 2018-06-15 8:07 AM, John Kearney
wrote:<br>
</div>
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