Andy Nachbaur asks for more details on when not to treat for Varroa.  The
information is based on a study in the UK so it may not relate directly to
conditions elsewhere.  I am reluctant to debase a useful scientific study by
cherry picking from the results and readers are recommended to obtain the full
document from the Central Science Laboratory if they are interested.
However, a table in the pamphlet indicates the estimated mite population level
below which no control measures are needed during the current year but
monitoring must be undertaken the following year.  January to May - below 170;
June below 300; July below 500; August below 1000; September below 2000;
October to December below 2500.
I think it might be helpful if US State Apiarists contacted Dr Martin to
discover to what degree the model can be adapted to local conditions.  Tel UK
01904 462510 Fax 01904 462240.  He probably has an e.mail address but I don't
know it.  There probably is a way of finding it but I am too much of
technophobe to have been able to find out how.
Chris Slade