Hi Ruth
Very often the answer to a question like this is in the Bee-L archives.
I searched for "autumn invasion" and found
I strongly suggest that you
carefully read the discussion in the freely-downloadable paper by Frey and
Rosenkranz, "Autumn Invasion Rates of Varroa destructor (Mesostigmata:
Varroidae) Into Honey Bee (Hymenoptera: Apidae) Colonies and the Resulting
Increase in Mite Populations."
In their study, there was little reason to suspect the presence of
collapsing colonies in the vicinity, yet mite pops skyrocketed in colonies
in the high-density area after effective treatment completed on July 26th.
PLB
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