Store plastic boards flat. on a flat surface and out of the sun. I store extra boards outside between two outter covers. If you leave them on an edge, the boards will sag.
Do not smoke your hives, this creates an unnatural mite drop. Insert your oiled sticky. Wait 3 day and try to remove it the same time of day. You will see a variety of debris such as wax, pollen, mature and immature mites. The mature mites are small, oval, and dark reddish brown. The immature are beige, almost transparent. Under a magnifying glass, you can see tiny feet. Count only the mature mites. We were using a random grid, but lately we draw a big cross on the board, right through the oil and debris, and then divide that area again into 4's to make counting easier. Just count one of the 4 squares. This is not scientific, just quick and easy. Take that number, multiply it 4 and then divide by the number of mites by 3 (for 3 days). We start getting concerned when we have a mite drop of 30 mites in 24 hours
#3. Remove the board entirely.
There is a study from Canada by Jean Pierre Chapleau, 'Les Reines Chapleau', where they found open bottom boards in cooler wet areas actually increased the varroa mite population to almost double due to the cooler conditions delaying the hatching of brood and allowing the mites to reproduce again in the capped cells during those few extra hours. The report also said there was a great success with hives kept in warmer, dryer areas of country. We give you that option.