Bill writes:
>We know that they increase the efficacy of a Varroa treatment (Delaplane
>et al), even when the bees exhibit resistance to the treatment!

I don't think we know this at all. I don't think *one* study proves a
single thing. It has to be replicated.

>We know they are a good tool for easily checking mite levels.


I don't agree with this either. I think there are a variety of
factors which make the mite drop an unreliable index of overall mite
load. One is: how close to the bottom is the cluster? If it is close,
you are apt to see more mites on the bottom than if it is higher up


>We know that there might be an increase (French-Canadian study) in
>Varroa over winter but not sure since the data was not statistically
>significant.

I am sorry, but I equate the words  *not statistically significant*
with *this doesn't mean much at all, so don't jump to conclusions*.


>We know that screened bottoms lead to increased brood production

I don't think this has been proved . In the trials I participated in
there was no increase in honey production and no decrease in mite
infestation. We didn't measure brood but if there was a significant
increase in brood it should have created an increase in honey later.

Screened bottoms are being touted as "part of an IPM program" but to
be part of a program they have to have some *measurable effect* that
is dependent on unique circumstances. I think people like the idea
because it is easy and you just do it once. Annual requeening with
improved stock is much more of a chore.

--

Peter Borst <[log in to unmask]>