Hello Barry,

>>...why there are no varroa on your exposed drone pupae...

I've treated my broodless colonies in late fall with oxalic acid and 
have found it very effective.  

>>if the lack of varroa is the reason ferals are coming back...

The return of the ferals and little varroa evidence in my hives are 
unrelated for the most part although I've been raising my own queens 
that with local drones for the past 3 years.

In my opinion, varroa had reduced the feral colonies and now it 
appears the survivors are staging a comeback.  The fact, that the 
feral comb averages 5,0 mm cell size, I believe, helps the feral keep 
varroa reproduction down at the end of the season.  The smaller cell 
size is towards the bottom of the comb sections where the last 
generations of workers are raised before the winter.  It's critical 
to a colony's survival to go into the winter with low varroa loads.

The other factor may be smaller populations in feral colonies.  
Managed hives lead to greater brood rearing which provides varroa 
with greater opportunity to reproduce.  And varroa will outreproduce 
bees if unchecked.  This is in line with what queen breeders like 
Kirk Webster report.  Namely,  they are able to keep nucs without 
treatment year round but still often see untreated full size hives 
collapse.  Kirk Webster selects for varroa tolerance among other good 
traits.

Waldemar

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