Such as "cascade" was clearly observed after the invasion of varroa into most countries.  As colonies began to collapse, the remainder were overwhelmed by drifted mites.  I've seen this occur myself.

I was referring to a seasonal cascade her in the US .  If the effect was due to mite crashes,  they would start earlier in the season in the south as they are ahead of the northern states in brood/mite development.  




Yes, was a small portion, likely unrealistically small if it were to be applied to a typical apiary, in which drift of workers occurs to a much greater extent.

The  2.5 number was the amount that successfully emigrated from any one hive,  why do you think it would be any different in a "typical apiary"???




I don't know why you chose 1 in 40.  

Typical yard size I was referencing the test method there,  not total mite levels.  Our test protocols need to be a bit better than the 80% confidence level was my point,  but we can probably live with something less than 100% confidence in the check system not how many hives are typically high mite loads.






>The problem with that is that its usually just one or two hives doing the robbing

I've long wondered about this.  Do you have evidence do you have to support this claim?

Just observations.  Seen it a few times.  Once a "robby" hive gets in  the seem to turn it into a group activity.  I see it here at the shop also.  One hive or two will figure out how to crawl under the door,  or in a crack to get inside  and will rob honey from the building. Follow them back and its typically just one hive  the other hives in the yard being at work with normal foraging.   It does seem different in a dearth when they will all do it,  but there are many times its just one or two hives seemingly.  I have moved a couple of hives from the home yard when they get that way.  I keep some smaller hives in this yard and robby bees are an issue.


Charles

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