I do try to burn the dead litter from under and don't compost any stalks on the allotment (one or two at home but that's not an issue as I only have raspberries and a few lettuce really at home). Prevention seems beyond me.
I read about using cardboard with grease or treacle on so they jump onto it and stick, I happened to have some grease bands left over from doing the apple trees and well they were a right royal pain to put on the trees but work really well at catching the mites. I've been catching maybe 20-40 per session ( as often as possible but not every day). How long before I can really see a difference- are they like slugs, there in the millions, or is there a chance I can beat tehm down like this... or even another possible approach?