There have been several new methods of varroa control mentioned
recently, including powdered sugar, smoke, and FGMO. Each has Varroa
drop as a feature of its efficacy. Different smokes appear to both cause
Varroa drop as well as Varroa death while the other methods seem mixed.

It has been mentioned that the some methods cause the varroa to slip off
the bee because of the medium used. That may be true, but it seems to me
to not be the probably mechanism. I would postulate- a scientific term
for guess- that varroa drop is caused by an inbred survival reaction by
the varroa. Sort of on the same order of the reaction by bees to smoke.

Varroa are not always loosely attached to the bee, but often wedged in
as well as parasitically attached. I question if they would fall off
easily because of bad footing.

Let's look at the results of sugar dusting. If the dust particle are too
large, the dusting is ineffective. But, from what has been posted,
atomized FGMO and various smokes cause varroa drop. All are of small
particle size. Smoke has nothing to do with varroa feet, but all can get
into the mite breathing system. Reduce the size of the sugar particles
and it can too. And the results are the same, varroa drop. The reason
could be because of a clogged breathing system or some other survival
mechanism.

All this is leading to the simple conclusion that particle size and its
persistence may have as much to do with varroa drop as the material
used, including, to an extent, smoke. Have an irritant of the right size
and you get Varroa drop. It would be fairly easy to disprove.

As far as open mesh floors, if Varroa drop is the result of each, then
the cheapest mechanism is smoke injected through the open mesh floor
since all the other methods require opening and manipulation of the
hive. The only thing you would need is a method to uniformly cover the
interior with the proper amount of smoke.

But. I see it as an exercise for a hobby beekeeper and not a commercial
alternative except as something to be done in conjunction with other
methods. It would require too many trips to the apiary and labor is not
cheap. I doubt if many commercial beekeepers will shift from simple,
effective, and reproducible one treatment chemical methods to the many
treatment labor intensive methods required with open mesh floors.

The future of Varroa control is still in the bee and the mite. Change
either and the problem is solved. SMR, hygienic bees, and maybe even
cell size are the true future of varroa control.

Bill Truesdell
Bath, ME