>> The key point about "IPM" is that one
>> must know pest population in terms of
>> how much damage the pests will do.
>> The dead-giveaway with varroa is that
>> their population growth starts to "go
>> exponential" or "spike", and the resulting
>> increased population of mites is what
>> "overpowers" a colony."

> Is this strictly true as written?

Yep.  The "slope of the curve" is the only practical way
to accurately monitoring mite populations, assuming that
one would rather use a sticky board alone than both count
both mites and estimate bee population for each hive monitored.

I'd submit that trying to estimate bee population is counter-
productive to the process, and one is better served to spend
the time counting mites more often and with more care, ignoring
the bee population entirely.

Anyone who expresses a threshold as an arbitrary integer is
talking down their nose to you, and thinks that you are too
stupid to comprehend, or too lazy to make multiple measurements
over time.  The dead giveaway is when all the handwaving starts
about "strong" versus "weak" colonies, rendering the integer
not only useless, but misleading, and thereby, counterproductive.

> European researchers seem to say it is not generally the
> mites that cause colony collapse (bees are weakened but not killed )
> but the associated increase in viruses.

This is true.  Mark Feldlaufer of the USDA Beltsville Bee Lab
recently hired on Judy Chen, an card-carrying microbiologist, who
promptly sat down at the keyboard of a PCR machine, and started
looking for viruses in individual mites on individual bees, and
gathered data that shows a direct correlation between the number
of mites on a bee larvae and the incidence of virus transmission
between all the mites.  The poor little mites are infected THROUGH
the bee.  The paper is still "in the mill", but has the title:

        "Molecular evidence for transmission of Kashmir bee virus
        in honey bee colonies by ectoparasitic mite, Varroa destructor."

It will be in "Apidologie".  No idea when.  Its "in press".  The
authors are Chen, Pettis, Evans, Kramer, Feldlaufer.

The interesting thing was that by the time one had 4 mites crawling into
a brood cell, the game was over, in that there was a 100% chance of all
4 mites (and the bee larvae) exiting the cell with viruses, with the mites
presumably going on to spread the virus(es) to more mites via bees, and so
on. Very impressive, to be able to detect viruses in a single mite at a
time.  (Mark brought a nice set of slides on this at the last MD/VA joint
meeting of the beekeepers.)

> It has been posted that mite populations are larger in large
> colonies. Is that true?

It cannot be true in ALL cases, as it is certainly possible to
have a large colony with no mites at all.  It is correct to say
that a larger colony can "carry" a larger number of mites as an
insignificant fraction of what would prompt treatment, and
that this same exact number of mites might prompt treatment
in a smaller colony.

> The concepts of economic threshold and economic injury level
> are interesting but are these the most helpful for beekeepers?
> Economic Injury level suggests we wait until the reduction in
> injury exceeds the cost of treatment - but that could apply
> when injury has reached a high absolute level...

One must still factor in the reproductive ability of the current
population and the future impact thereof.  Its not like one is
expected to wear blinders to the future.

> Do we not need to consider the 'most cost-effective intervention'.

The big decision is pulling colonies out of production to treat
them (or using Sucrose Octanate, if one has a free afternoon to
treat a mere dozen colonies).  In some cases, a true hardnosed
"Cost effective" strategy may be deciding that the colony is doomed,
yet leaving it in production, based upon the premise that the honey
harvested will more than pay for a new queen to head up a split made
from a healthy colony.  The problem is that letting the colony collapse
isn't really "keeping" the bees, is it?


     jim (The power of accurate observation
          is often called cynicism by those
          who lack it.)

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