In a message dated 13/10/01 05:12:10 GMT Daylight Time, [log in to unmask] writes: << If I still have to treat with chemicals every spring and fall, what's the point of replacing all my bottom boards? >> Peter, Do you really need to treat twice a year? I have only ever treated once a year. This year, a year after last treating, the mite drop on hives on open screened bottoms was between 2 and 12 in 24 hours, the majority being in single figures. So I didn't treat them this time but will test again every so often to avoid unpleasant surprises. Chris