Hi Matthew,
I would suggest directly emailing Megan Colwell, PhD candidate in Rob Currie's lab at U of Manitoba. Please let us know what she says. She presented on this topic in the fall at the BCHPA AGM. I haven't been home to review my notes for you since you posted this. If I remember correctly, she was looking at longevity of different viruses on comb and the effects of irradiation. Every virus seemed to have a different lifespan on comb and reacted to irradiation differently so the results aren't easily summarized from memory.
From personal experience, I had a situation with DWV several years ago that is similar to what you seem to be experiencing. I had a few hives that were very heavily infected with DWV, as indicated by a large number of bees with shrivelled wings, despite the fact my mite counts weren't great but also weren't too insane (around 3% in late August). I felt like DWV somehow gained a life of it's own in those hives.
I chose to irradiate my equipment, largely because I also had hives collapsing from a brood problem I was never quite able to identify (PMS? Atypical EFB? Viruses? Something contagious and nasty and not AFB, sacbrood, nor typical EFB, as far as I could tell).
Over two years, 2014 and 2015, I irradiated virtually every frame I owned. I had the healthiest bees imaginable for 2.5 years, with no signs of brood diseases in my hives again until August of 2017.
Purely anecdotal, I know. Maybe the infection cleared on its own, simultaneously to my irradiating the equipment. Maybe I'm seeing diseases again now because there is a 2-3 year cycle of health followed by disease. I am planning to irradiate again this spring, however. I believe irradiating broke the spiral of weak colonies and poor health in my apiaries by reducing the pressure from a whole host of bacteria, microsporidium, and possibly viruses. But who really knows? Possibly Megan Colwell.
I hope that helps.
Tracey
Alberta, Canada
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