I counted five in that photo, not a huge amount. There are a number of reasons that colonies fail that Ceri (mbc) has already mentioned.That’s useful, thanks Simon.
Not sure what to make of it then? I was expecting to see loads of mites if we’re thinking it was varroa that destroyed the other colonies...the hives are all close together with only about 18 inches between each one.
I used a gas vap to vape my bees whereas the other guy used a wand type device. I’m pretty sure I used the gas vap properly (it was my first time using it but I did a test run outside the hive first and all seemed well). If anything I left the nozzle in the hive for longer than the recommended amount of time....probably just over a minute. I can’t imagine this would make it less effective though....?
Cast swarms are an unknown provenance, nice if all works out but it often doesn't. You used OA strips as varroa treatment, we've done that for two years with no dead outs so far but that's with bees monitored for a number of years so we made an informed decision.