> This trap or another method that prevents fallen, viable mites from returning to the hive is recommended as a part of an integrated control program.

When I worked at the Dyce Lab at Cornell University we tried for about five years to get bottom screens to work. We wanted them to work, but they never did. They never affected mite buildup, honey production, brood, overwintering, neither negatively nor positively. No significant difference was ever found. 

Now, there may be the issue of signal to noise ratio. If the hives vary too much, a small effect may not be noticeable. Scientists try to eliminate this variation by either starting with "identical" hives, or by increasing the sample size. Of course, the best results come from a technique that really works. A strong effect tends to be noticeable despite the variation (noise).

I always objected to including screened bottom boards in IPM recommendations. I think it is wrong to recommend something that *doesn't do anything*. 

PLB

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