>
> Given what we all know about the effects of selective pressures on
> populations, is it not a concern that by widely using drone sacrifice to
> control Varroa, we are inadvertently applying a selective pressure on
> Varroa to push their genome toward one which infests worker brood at higher
> than present rates (since they are overwhelmingly the ones left to
> reproduce)?
>

I'm not able to answer this question, but hopefully someone else on here
can (as it interests me).

>
> However to get back to the drone contribution discussion, my main
> objection to drone sacrifice is that it represents a huge drain on colony
> resources. In our short season here, that is one more obstacle to success.
> And, widely practiced, it means fewer drones in the local DCA's, which is
> important to me when I go to make my own wild mated queens. Note that when
> I push my drone production in the best of my colonies, it is after ensuring
> there are low Varroa levels.
>

For one, I think it's a fallacy to believe that you can prevent colonies
from rearing drones. If you don't give them a drone frame (or an empty
frame), they'll inevitably find a suitable space to rear drones on their
own, either in the form of burr comb, spaces here or there, damaged corners
or edges of comb, or worse yet I've seen them build drone comb over worker
foundation. Sure you can restrict it, but not prevent it.

But more to the point, a certain percentage of drones, and drone comb, is
healthy to a colony (I've read it before, but can't place my fingers on
it). And some studies have shown that an increase in drones doesn't
necessarily decrease productivity of the colony:

"Allowing colonies to rear drones freely would therefore appear to have no
detrimental effect on their economic performance, and the need to restrict
drone rearing as a beekeeping practice may be questioned."

The Effect of a Plentiful Supply of Drone Comb on Colonies of Honeybees, by
M. Delia Allen, Journal of Apicultural Research, Vol 4, 1965 - Issue 2.
Although I don't believe the same conclusion was found in some other
studies, primarily by Dr. Seeley. (
https://www.apidologie.org/articles/apido/pdf/2002/01/Seeley.pdf?access=ok)

I also believe a colony is significantly better at regulating colony
resources in the form of drone populations (on average) than I am. I've
never known a colony to raise a frame's worth of drones simply because I
put a drone frame in there (as they'll fill it with food if they don't want
drones), but freely fill the frame when they think they need more drones.
They are always quick to rear drones when dandelions bloom in spring, and
quick to remove all drone larvae/pupae when a dearth appears.

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