>Aren't we in danger of the development of terra-resistant AFB/EFB using
>"extender patties" with TM?  The patties at least violate the "long term
>exposure" concept, do they not?  The advice I've seen on Terra patties
>is "whenever there are no supers on."
 
I believe this is of genuine concern.  And yes, it certainly could fall
under "long term exposure."  Ideally, the patties are gone or removed when
the honey supers go on.  I get rid of what is left of the patties when the
first supers are added, but have seen where some commercial beekeepers just
leave them in, and they are still there when the supers are harvested later
in the year!  This refers to the pre-formed "Terra-Patties," BTW.  Can't
say whether it would be the same with some other formulation, such as that
using the TM25, granulated sugar,etc.
>
>Alternately, the terra and powdered sugar directions I've seen are to
>apply the powdered mix around the perimiter of the brood nest (top of
>the frames) 3 times, 7-10 days apart (with supers off.)
>
>I haven't seen the "never cleaned up" problem with the powered mix
>someone mentioned here, but I also didn't know about powdered sugar
>containing cornstarch. Is that *harmful* to the bees, or simply of no
>use?
 
Not sure. Since TM is a powder, perhaps it just combines better with the
more starchy confectioner's sugar, and so is applied with that.
 
Exposure to the antibiotic might not be so different between a small
extender patty (lasting 3-4 weeks, say) and repeated dustings over the same
period.
 
On the cleaning-up, sometimes a weak colony (or nucleus) won't consume all
the dust in a week, so you can end up with a dried crust of TM/sugar powder
stuck to the frame tops at the perimeter.  The amount left over this way is
normally just a very small portion of the total amount that was applied.
.........
 
A bureaucrat in the USDA noticed one of his subordinates sitting glumly at
his desk, head in hands, and sobbing.
 
"What in the world is wrong, Jenkins?" he asked.
 
The man slowly looked up, his face sullen with somber expression and
replied,  "My farmer died!"