> But I've never known or seen a hive collapse (or dwindle) as a result of virus loads, DWV in particular, or have the virus levels grow exponentially, independent of having excessive mite loads.

This keeps coming up. How would you know? No deformed wings? Unfortunately, deformed wings is not a reliable indicator. Sure, they can indicate presence of advanced infection, but I have posted several times about "covert" infection, which may not do anything but kill off the colony prematurely. In 2016 a lot of us controlled mite levels and yet lost up to 80% of the colonies in fall (before winter). 

There were no symptoms other than premature collapse, in some cases very large colonies. I did have a hive sampled by researchers and it showed very high virus levels. That wasn't even the first one to go down, it hung in there until about February. I believe the sudden fall die-off was caused by covert viral infection, without the presence (at the time) o varroa mites. 

Now, they could have brought the colonies to this point by crippling their immune systems and encouraging massive viral replication. I have no evidence, nor proof of this taking place, of course, since I don't feel like coughing up the money to have my bees routinely sampled for viruses. There's no treatment for viruses anyway, unless you believe the advertising hype (I don't).

PLB

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