Video of Dr. Greg Hunt of Purdue University, Dept. of Entomology speaking to the Southeastern Indiana Beekeepers Association. He talks a little about pesticides, but what really caught my interest is that he's been selectively breeding for bees that will chew the ankles of varroa mites.
His experiences seem to suggest that finding mites with chewed off legs on the bottom board may correspond to hygienic behaviour in honeybees. After selecting for this behaviour, very few of his colonies require mite treatments.
Dave and Jon and both certified master beekeepers. They are from Illinois and Arkansas respectively, so the show offers the perspective of both southern and northern American beekeeping. This podcast is recorded live and the audience is welcome to log in online or phone in with questions.
To get a sense of the style and format have a listen to episode six where they discuss mite management:
A study performed southern tip of Gotland,an island in the Baltic sea where 150 colonies were left unmanaged with varroa mites. After 6 years it appeared that a host-parasite co-adaptation occured with the 5 colonies, plus an addition to 8 swarm colonies that remained.
Original discovery of feral bees co-existing with varroa
A 2007 study by Seeley looking at the honeybee population of the feral bee population of the Arnot Forest showed a stable host - parasite relationship with the varroa mite.
An interesting part of this paper is that it describes how survivor bees co-existing with varroa were taken out of the Arnot forest and inoculated with mites from another apiary. As mite growth in inoculated colonies occurred at a level consistent with control colonies, we might guess less virulent mites have evolved in the unmanaged bee population of the Arnot forest.
Genetic analysis of the Arnot forest survivor bees
In 2015 Alexander S. Mikheyev, Mandy M.Y. Tin, Jatin Arora & Thomas D. Seeley published a study showing that the mite resistant bees living in the Arnot forest are genetically distinct from the bees in the nearby apiaries. They also compared genes of current bees with museum sample of Arnot forest bees from the 1970's. This comparison shows there was likely a genetic bottle neck, and Arnot forest bees have evolved distinct traits as compared to the bees living in the forest prior to varroa. It also suggests that some influx of some amount of new genetics has occurred in the population, including those associated with africanized bees.
In 2011 David Heaf put together a fairly comprehensive review of different scientific studies on the usefulness of using small cell comb as a varroa control. While a few studies found positive results, particularly when africanized bees were used, the majority of the studies did not find small cell beneficial against varroa. Of course some questions still remain.
I first noticed bees with deformed wings virus(DWV) crawling around in front of one of our stronger hives in the late summer of last year.
We treated in the fall, and by spring symptoms had dissapeared. It was the strongest of our twenty hives this spring and we had to split it to try and keep it from swarming. By late summer(Sept. 1st) I once again started noticing bees with deformed wings. From this point in the season on, anytime I looked, I was able to find at least one if not a handful of damaged bees crawling around in the area directly in front of this one hive.
Bees with deformed wings are expelled from the hive and typically have a life span under 48 hours. Seeing large amounts of DWV is a clear indicator a hive is suffering from a serious varroa problem.
Bees with DWV may also have really stubby short abdomens. In some cases I see the short abdomens without necessarily seeing visibly deformed wings. I believe these stubby bees with healthy looking wings, are also incapable of flight.