Let them land and then vacume as many as possible may take few hrs or days but you will get the bulk if em lol, do not leave anything uncovered big enough for them to reach the batch, (I have wrapped air locks with plastic wrap and poked smaller holes so they wouldn't get in and it still can vent) then take a few small containers add Apple cider viniger and a small drop or two of dish soap (i prefer un scented but anything in a bind works) it will attracted them they will fly in and get stuck and drowned empty every few days, just place them around that room it works just mite take a few days