50 years, most with low wintering loss in Western MT. When we lost colonies, it was whole colonies. Any colonies alive in the spring had laying queens. Due to harsh winds and cold snaps in February, we wrap in black roofing felt. Our days tend to be overcast. Most winter days are surprisingly mild, but winds coming down from Canada can wipe out unwrapped colonies.
Last four years, we've lost wintered colonies due to queen failure. We put strong colonies with good populations, started from packages, and new queens into wraps. Mite control, regular health inspections, all done, as we should. In mid-winter, the queens are either slow starting to lay or aren't laying at all. We normally saw queens go back to work in Feb, no later than mid-March. For the past four years, that's not a given. Worse, queens that start laying, go for a few weeks, then stop/disappear (late winter, early spring). Unfortunately, that happens before the queen breeders on the west coast have any queens to ship. By the time we can get replacement queens, all of the colonies have failed due to either no queen (lost sometime during the winter) or queen failure (no laying, no sign of queen) in spring.
I will have been at this for 50 years (as of August, 2023). Our winters used to be much more severe, and we rarely lost more than 5% of our colonies. Even with mites, we rarely went over 15%, except for those that we intentionally exposed to pesticides, Nosema, IIV. The last four years, only about 10% of our colonies were viable by first bloom.
I have never before seen first year queens in strong colonies disappear/fail before spring. We have lost a lot of forage diversity at our primary yards (Missoula has grown out around us). So last year, we found new yards where forage was diverse and plentiful. Went into winter with ten strong colonies, came out with two. Replaced with new colonies from packages, and the queen loss has already shown up in 50% of them since end of Sept.
Jerry
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