I am about to publish a book about beekeeping and I like to share an unedited version of chapter 4 that may help some of you to keep the V.destructor mite under control. a few beekeepers here use this method and it works very well. It does not need any product but good management and proper (accurate) timing, which is all described.
It also describes the method of using formic acid, but it is not needed if you follow the instruction. ADMIN EDIT -> attached PDF below
You will find other information with above search, e.g. how to process wax and build your own foundation.
Please ask me questions.