I have observed that the topic of mite-resistance in feral/wild populations comes up when discussing how one can "start" with better stock. I have noticed, that even with the initial brood break from the swarm as well as a potential summer split on said swarm, that there is a speculative 50% attrition rate on caught swarms if left untreated. My observation is that the earliest caught swarms seem to have a higher likelihood of coming from non-beekeeper/kept colonies in my area.

I evaluated 48hr mite-drop (72 was unobtainable, they were eating the drop board!) on a recently acquired swarm by administering a 2g dosage of OAV in a 2 medium 8-frame Langstroth box on day 4 post-hiving. I wanted to know what number this represented if I were to estimate the Varroa load of the donor colony, was this possible?

Randy Oliver's Varroa Model would estimate the hive survival sans treatment in my Michigan region with estimated neighbor/mite pressures to at least March the following season but would likely succumb to the Varroa in spring (a likely outcome in volatile Michigan spring/winter). The survival is also being estimated on at least 80% of the Varroa being reproductive. Now this does not measure any level of resistance in the colony per se - and bares further testing. I arrived at the question of a hypothetical approach to determining if additional testing was necessary or if re-queening should be my first priority (considering my optimal management model is to not be dependent on varroacides as a mite mitigation strategy) under these circumstances. 

1. If the donor colony was speculatively "wild" would that colony's resistance levels be measurable based on the prime swarm Varroa load?
2. Would an OAV treatment during this broodless period provide measurable data that allows for a reasonably estimable Varroa population in the donor colony?
3. Can I reasonably model these Varroa infestation numbers in making decisions on whether or not the donor colony's genetics and queen are worth proceeding further with evaluation and testing of resistance in order to save time and resources?

A good entry on the topic from the Apiarist led me to a research paper. Both readings gave me some insight into the potential for this as a measure of evaluating Varroa tolerance/resistance in donor colonies. Obviously there are caveats, but I would assume judiciously, that a donor colony with low Varroa numbers are expressing measurable resistance in some fashion. Even if the low infestation numbers could be post-beekeeper treatments, it would provide one with time enough to engage in assaying or monitoring Varroa numbers via wash with which to make an informed decision. I would be looking for more than just VSH per se, that would be one outcome, but also tolerance overall? Some colonies are managing higher loads than others in my apiaries and not crashing, but I don't feel comfortable when they are trending over 5%...

So if it wasn't clear, my base question in this is: Can I reasonably decide if additional evaluation of a swarm colony is warranted when seeking local/wild resistance genetics based on initial mite-sampling data prior to brooding and increased mite-fecundity? What are some thoughts from the community? I do not feel that recommending people  "start" with swarms as a resistant/tolerant source of bees is a sustainable approach - it is a piece of the puzzle, but not necessarily one that can provide a solution without some effort and assessment....

For reference:
https://theapiarist.org/swarm-and-mite-partitioning/
https://www.tandfonline.com/doi/abs/10.1080/00218839.2005.11101177

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