Jim said
I dunno how to stop bees from "drifting" when hives are clustered in groups,
but it seems clear that if we could somehow reduce drifting, we could reduce
reinfestation.

Drifting drones surely spread varroa mites but the main cause of
reinfestation is *robbing*.

As hives dwindle because of high varroa infestation they become easy prey
for robber bees. I have seen worker bees with many varroa hanging on land on
the landing board when the robbing of a varroa infested hive is going on.

Many beekeepers had to treat several times a year when varroa first arrived
due to  reinfestation.

In other words the varroa were piggy backed to the hive which was doing the
robbing along with the honey. Enough varroa to push a hive over threshold
could be brought back.

Bob

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