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Subject:
From:
Murray McGregor <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Tue, 18 Apr 2000 08:04:33 +0100
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>I agree, but you need to correspond with people in the central valley of
>California and up into Oregon, where it is much warmer than Scotland (or
>Oklahoma, or Colorado, or Tennessee) in the winter because of the Japanese
>current, and where a great number of nervous people live.

My correspondence with people in Africa and South America does not give
any grounds for assumming that temperature is the key factor. In all
these environments they are capable of withstanding reasonable periods
of cold (even very cold) weather.

In some mountain environments where cold is a relatively common
occurrence scutellata or AHB are well established, yet not too far away,
but beyond a relatively stable boundary, conditions can be much more
benign, yet there is no ESTABLISHED scutellata or AHB.

Of course these places mentioned need to be wary. It is quite probable
that AHB will be found there, either from natural migration (such as
Bakersfield that was mentioned) or from migratory beekeeping. The point
is that if, in their natural range in Africa, or what must now be
considered a natural range in Argentina, beyond which they do not seem
to be able to establish long term, is now more or less fixed at or
around a certain latitude, and the low to mid 30's appears to be it,
then why should North America be different. I have heard the arguments
about the relative sophistication of American beekeeping, and the level
of winter feeding and care, making the situation special, but that is to
underestimate the capabilities and methods of those in South Africa and
Argentina, where they are also migratory and must prepare bees properly
for winter.

People in those countries are your most relevant source of information
about what will ultimately happen.

I agree that I cannot have ANY definitive opinion of what AHB is going
to do in your country, as Scotland is unlikely ever to be affected, but
while you were on the subject of maps, one was published in the bee
press a few years back (one of the american journals, I forget which)
which illustrated the spread of AHB in the Americas, and there was
another showing the range of scutellata. In the south the latitudes were
very similar.

Climate must be a secondary factor as the limit is not a straight
latitude line, but something akin to seasonality must be at work in this
case. We may never know exactly what it is.

Incidentally, Scotland is a country with a relatively mild damp maritime
climate, a bit like your western seaboard from Northern Oregon up into
British Columbia. We NEVER get cold approaching the horrendous 70+
degrees of frost you mention for Arizona, but then summer heat over 80
degrees is also rare. At our latitudes we should be a lot colder in
winter were it not for the Gulf Stream (North Atlantic Drift). In our
home area we have only had lying snow for 5 mornings all winter this
year (it is usually more). A lot like your mention of the affect of the
Japanese current in your own country.

Throwing in the latitude factor as a likely limiting factor was not
something I arrived at independently (a large amount of correspondence
with beekeepers both in Africa and North America took place at the
time), nor is it meant in any way to be some kind of definitive
pronouncement on the issue. It is meant more as a discussion issue than
anything else, but it may also indicate that the scare stories of the
whole of North America being swamped by AHB are not actually the likely
outcome. Despite the migratory beekeeping, and your relative
sophistication of management, the spread has slowed dramatically since
its arrival in the southern states.

The question you need to answer is why. Is it due to your levels of
surveillance. (Do you really think you are catching almost all such
swarms?) OR, is the natural, as yet unknown, limiting factor starting to
kick in and arrest their rapid progress north. I guess that in 10 years
the line will be relatively stable with seasonal incursions across it.
Only then will you know.


--
Murray McGregor

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