Peter Borst wrote:

> We used coumaphos in fall of 2000 & spring 2001. That fall mites were
> acceptable, so we went back to Apistan fall 2001 & spring 2002. It hasn't
> worked, so one wonders: 1) did the coumaphos not knock out resistant mites?
> 2) did we pick up resistant mites from other hives? 3) did environmental
> conditions cause this rapid build-up?

When Cumophose resistance was discovered in Maine, Apistan was used
after the Cumophose to see if there was any mite drop, and there was.
But the mites were not killed. They did drop with the Apistan but were
still alive so could reinfest (which is one reason I wanted to try
screened bottom boards). So the mites were both Apistan and Cumophose
resistant. I am not sure if they had the same period of non-apistan
treatment as yours, but my guess is they did.

Bill Truesdell
Bath, Me