These are just a few of the great results at the 24 hour mark. We arrived at a very hygienic bee by selecting for Varroa tolerance. Dr Royce from OSU came down and showed us how to to the freeze killed brood assay. There were some that did not get 100% in the test so I presume they must have other mechanisms for coping with mites. I have been leaning towards the ones that got 100% for the last few grafts but will continue to monitor the other breeders for mite loads and overall success.
The one labeled 13.1 actually cleaned both sides of the comb. I think we may have used too much liquid N and froze it all the way through.
That amazing! I gotta try that method.
Good work! Another person that did this for years was S. Taber, don't see much mention of his work anymore.
Where do you get your nitrogen, and what do you use to store it?
We used a loaner dewar from a local welding supply shop. I think it was about 10 or 12 liters.
is there any reason why "dry ice" wouldn't work for this purpose? I know it's plenty easier to come by for the average hobbyist/sideliner beek...hopefully it'd work well too?
What were the mite loads like? Does this indicate varroa mite tolerance or resistance? I can see how it would indicate hygenic behavior, but, does hygenic behavior directly lead to mite tolerance/resistance?
What other traits are you selecting for and how do you go about accessing the degree of those traits?
How did you get them to lay around that circle?
I am a nebee so i am just learning about the bees
The OPer can answer from experience, but, you start off w/ a nice patch of capped brood and kill what you can see as an empty circle of brood by applying liquid nitrogen, which freezes the pupae dead. Exactly how this is done, someone else needs to explain. I think a tin can is used somehow, but I haven't done it.
what is the relationship between a cell that has been killed by liquid nitrogen and a cell that has a foundress mite mite in it
The capped larvae that WERE inside the circles were killed with liquid Nitrogen, as sqkcrk said...then the bees removed the killed larvae within 24 hrs. This is done to test the efficiency with which bees will theoretically remove varroa infested/killed larvae from the comb, thus reducing varroa levels in the hive. (or at least that's my understanding of it)
I believe the freeze-killed larvae are supposed to be homologous to mite-infested/killed larvae to the bees... i.e. it's not necessarily "varroa" that the hygiene is sensitive to, so much as "dead larvae" sensitive hygiene...so the same trait should be pretty efficient against EFB too (once again, in my opinion, and according to my understanding of the principles in practice).
Thank you for the answer Robherc , i couldn't figure out what was going on from the start of this thread, now i understand.
The liquid N is poured in and then after it thaws the frame is returned and the clock started.
Varroa sensitive hygiene is a well documented trait and does result in lower mite loads. Apparently you can end up with very hygienic bees by selecting from bees that cope with mites well. It is a challenge to keep the selection pressure on but well worth doing. We are taking some steps this year to try to get these traits more "true breeding" throughout the whole population. More isolated mating yards and instrumental insemination will definitely be helpful this year.
Thanks. I can tell you've really thought about this. What are your plans? Queens for yourself or for selling to others?
Thanks for posting and keep up the good work JBJ
What is interesting to me is that you said "We arrived at a very hygienic bee by selecting for Varroa tolerance". My understanding is that Marla Spivak and Gary Reuter started the other way, breeding for hygienic bees by using the frozen NO2 test because of the strong correllation of hygienic behavior with bees that remain free of AFB. Yet they make no claim that MH queens are varroa resistant. What percentage of your breeders were that hygienic - if you don't mind sharing.
So, in addition to your bees having hygienic capabilities I suspect they have other positive attributes that make them varroa resistant.