> However, field anecdotal reports from beekeepers in the corn and canola
> areas do not support such an effect to any noticeable degree.

Actually, in my operation, varroa seems to have become more virulent 
over the last decade to where I gave up on using oxalic acid and went to 
Apivar.

Oxalic had worked for me for a number of years, but even after the five 
evaporations last winter, the levels were high enough this past fall 
that I gave up and inserted Apivar.

I have changed from wood to EPS and doubles to triples, ans changed my 
bee stock, so there too many factors to point at just one, but in my 
experience, varroa is getting harder to control.

As for the commercial operators on canola, in Alberta, they have a 
chemical control that works and use it as required, and therefore cannot 
gauge the virulence of varroa.

Regarding the quote, are you actually getting statements that they are 
not noticing increased virulence or simply that they are able to 
maintain control?

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