We live in the country and have a lot of problems with flies, both indoors and outdoors. We’ve tried homemade fly traps with vinegar – sometimes they work and sometimes they don’t. We’ve tried diatomaceous earth scattered in pet litter boxes with no apparent success. We’ve even put up the classic sticky tape traps which are only moderately effective. The one thing we’ve found that was successful were REDTOP brand fly traps. These are intended for outdoor use, but when they are first baited, they don’t smell very bad and I’ve used them indoors for a few days to cut down on the indoor pests. After a few days, though, they get a bit smelly and have to be relocated outdoors away from the house a little ways.
I put these up in early spring and forgot about the traps after the first week or two and was surprised when I drove the lawnmower past the large trap a month or two later to find it filled to practically overflowing. I went and checked the smaller ‘compact’ traps and found that they were just as full of flies. Truly remarkable! We will be re-ordering these traps come spring!