Hi Everyone,

Aaron Morris wrote in part:

" Peter mentioned that some of the hives were treated with
coumaphos, but my recollection of the presentation was that some of the
studied hives were started from packages and some of the studied hives were
established/over wintered hives that were treated with coumaphos PRIOR to
being used for the study.  My recollection (and I hope Peter will correct me
if I'm wrong) is that once the hives were entered into the study, all other
variables (such as mechanical or chemical controls for varroa) were kept to
a minimum (zero).  I believe the study attempted to examine solely the
premise that screened bottom boards and ONLY screened bottom boards can be
an effective means of varroa control."

Interesting comments Aaron and a possible source of variability in the study.  If some, but not all, of the colonies were treated with coumaphos before the test was the data checked for an impact of the treated vs non-treated on the results of the study?  Coumaphos is strongly absorbed into beeswax and is very stable there.  Just from observations of how long coumaphos treatment suppresses varroa populations, it is clear that there is a considerable residual effect of the coumaphos - i.e. the coumaphos in the wax continues to kill the varroa mites for a considerable time after the treatment strips are removed.  This would be an added variable in the experiment that would at least need to be accounted for.  This along with the relatively small numbers of colonies reported by Peter could explain the inability of the study to detect any effect on varroa mite populations in the test colonies.
I suspect the small ( 15% or so ) impact on varroa populations reported from other studies is below the detection limit of this study and so is not seen.
Now I do want to be clear on one thing - 15% reduction in varroa population increase over a season is not even close to being a "treatment" for varroa.  The research I have seen suggests that about 90% is what you need.   Open bottoms have other positive features as many have pointed out but their impact on varroa at a practical level, used alone, is not enough to help.  The colonies will still die.

One who has all his colonies on mesh bottoms and thinks the bees "like it" at least they will raise brood clear to the bottombar of the bottom box and even raise queen cells there.

FWIW

blane






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Blane White
MN Dept of Agriculture
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