>The reason is simple.  In the context of a pest/host
>ratio, counting only pests, no matter how accurately,
>is MEANINGLESS without a count of hosts.

Yes, the number of bees in a hive is a meaningful variable, but it's not 
the variable to trump all other variables.  We're talking about 
agriculture here: it's complex, and in actual practice we can't help but 
work with estimates, averages, and reasonable assumptions.  Sometimes our 
estimates will be inadequate, but we're talking about a margin of error, 
not meaninglessness.

It's not as if we have no idea how many bees are in a hive.  Worst case, I 
might fail to notice a substantial difference between two hives, one with 
twice as many bees as the other, but that's worst case (and probably a 
generous over-estimate, too), and the *average* variance is going to be 
much less than 2X, which means to me that we're working with numbers that 
are more than good enough for use in the field.  

Two winters ago I took all my 50+ hives and did 48/72 hour mite counts on 
all of them in early September.  Then I let them all go through winter 
without meidication/intervention.  With the exception of one hive that was 
noticeably smaller than average (i.e. I noticed *beforehand* and made note 
of it), the ~40% I lost were the 40% with the highest mite counts.  

After 3 years of testing all my hives, I have yet to experience a single 
winter loss (from almost 200 hive-winters) that couldn't have been 
predicted by the rule: >55 mites per 24 hours in early September unless 
the hive is dramatically smaller than average.

Are there special factors (variables) that could interfere with the rule?  
Sure.  Will I have hives that are big enough to withstand >55 mites?  I'm 
sure I will.  Could the 55 number be unnecessarily conservative?  Perhaps, 
but more than enough hives (on average a majority) come under that 
threshold for it to still be very useful.  Is every winter going to be the 
same?  Of course not.  Is every strain of bee and every strain of mite 
going to follow the same rules?  Of course not.  Are there going to be 
regional differences?  Sure.  In short, there are lots of variables, but 
they don't render the information we do have meaningless.

I haven't kept close track of the studies, but I'm roughly familiar with 
several studies that "proved" the value of thresholds.  Has there been any 
formal study to disprove the significance of one-time mite counts?  If 
there has been, I never heard of it.

So from my perspective, experience, good sense, and scientific research 
all strongly indicate that thresholds are a meaningful and useful 
management tool.

Eric

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