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Informed Discussion of Beekeeping Issues and Bee Biology

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Subject:
From:
Alan Goldblatt/Hilary Hamilton <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Wed, 22 Apr 1998 13:18:15 -0400
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Resistance to pesticides or antibiotics is inevitable if and only if the
substance is used incorrectly.  By incorrectly I mean either not long
enough (sporadically) or too long (continuously).  To avoid resistance it
is paramount to use the product according to the directions which are based
on the best research we have.
 
Let me explain how this works.  If you use a pesticide (or antibiotic,
which is really a type of pesticide) for a short period of time, you kill
only the most susceptible pests.  Lets say that by using terramycin for
only for days you kill the most susceptible 25% of the foulbrood bacteria.
That leaves you with the most resistant 75% which will reproduce happily
until your next treatment.  The next time, four days of treatment will not
kill as many bacteria because all the bacteria come from those more
resistant 75%, so you may only kill 10% of the bacteria in the hive.  Once
again you've killed the most susceptible and left the most resistant to
continue to grow.  In a very short time you'll have a totally resistant
strain of foulbrood.  This is why it's so important to complete the full
course of antibiotics when your doctor prescribes some for you.
 
Now, if you use the pesticide continuously you'll also develop resistant
pests.  This is because no treatment is ever 100% effective.  There will
always be a few bacteria which are totally resistant to the treatment.  If
you leave the terramycin in the hive all the time you will kill off all the
susceptible bacteria, and the totally resistant ones will reproduce freely.
 Now you've again got a resistant strain of foulbrood.
 
It may at this point seem that resistance is inevitable if you've only got
one method of treatment.  This may be the case, but if you treat properly
you can make it take a very long time to develop if it ever does.  The key
is to kill off enough of the disease that it doesn't easily bounce back,
but not so much that all you have left are resistant organisms.  You also
rely on the host (in this case the bees) to be able to fight off the
remaining disease on its own.  In addition, you hope that there remains in
the wild a reasonable quantity of susceptible disease, and that what
remains in your treated host may mutate and become less resistant during
the long periods without treatment.  It's a tricky balancing act.
 
So, the long and short of it is, if you use extender patties don't leave
them in there any longer than you'd treat with the dust method.  This info
applies to other beekeeping treatments too.  Don't leave apistan or menthol
in the hive longer than it says on their packages.  In fact, for diseases
like varroa which you can actually see, it's a good idea not to treat at
all until you actually see signs of a reasonable infestation.  I find that
I usually have no varroa in the spring, so I don't treat then (unless I
find some).  By the fall, I usually have a good crop of varroa in the hive,
so I treat for the recommended time period at the recommended dosage and
then remove the strips.  The bees generally do fine until the following fall.
 
With foulbrood you can't treat that way because once you have a real
infestation the terramycin won't work.  So you need to treat preventively,
ideally once in the spring and once in the fall.  Please don't treat more
than this!  I'll stop ranting now.
 
-Alan Goldblatt

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