I had a lot of mosquitos early in the summer, before getting the Thermacell's, and I also spent time spraying the yard and foliage I could reach with this garlic based stuff called Mosquito Barrier (mosquitobarrier.com), and feel that it certainly helped with mosquitos. Maybe it helped with flies too?
Even before we had the pavilion with 2 ceiling fans, I would put an oscillating fan or two out in the sitting area by the pool. I had two of those with a tall stand on them. I think a breeze, even if its from a fan, helps keep insects away.
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