>At our recent research meeting in Calgary, it was pointed out that, in Manitoba, a late October varrroa level of 12% was not considered fatal

Right, in fall that might not be too high, but in early spring a hive with a level like that might have a difficult time building up. I don't know how many of those 12% (approx 2400 mites) would still be there in spring.

>High levels is *precisely* what we were looking for.  We don't care much about low levels and we are not doing academic work.  We are doing IPM.  We are watching for levels that demand treatment soon.

What would be high level in March? What about April? Without figures to compare how can one say it is high or low? Is 12% high in Spring, or can you skip a Spring treatment with this level? You detected zero mites. We assume that there are mites, though, but we don't have any idea how many, right?

I would think 12% would be a pretty high level in April and would warrant some sort of Spring treatment to prevent a crash in mid-summer. I had one yard of 16 that was not treated all year (2001). August levels were 2 to 30 ( approx. 1 to 10%). By October, they all crashed. Not one was strong enough to winter.

IPM is *not* wait until they get till 50% and then treat. This may be already too late, particularly if virus Parasitic Mite Syndrome is already in place. How can a hive build up if it is riddled with parasites? IPM (as I have been taught it) is about determining safe levels of pests and treating with whatever means necessary if these levels are exceeded.


pb