Any great tips on defeating the "lovely" black flies that are so prevalent this time of year? We can't garden w/out them swarming our heads and biting us. The bites itch as bad as mosquito bites! I wear a mosquito net over my head but they can crawl through the openings and get inside. We spray our hats and clothes with Cutter, with DEET, but it doesn't work for more than an hour. Do the Bounce dryer sheets really repel them? Any advice is welcome!