Hi Steve, my brassica's especially the sprouts are covered in them, some say strained rhubarb leaves watered on them, others soft soap but I might go for the long winded way, grease or vaseline a large piece on wood and hold above the plants and shake them and the white flies stick to the grease when they fly up, repeat over and over again, I told you it was long winded. :-\ ;D ;D ;D