I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
I suggest you first try to figure out what is attracting the flies and eliminate it. Trash cans, animal manure, etc. are common causes of such an extensive fly problem. There are fly baits that are granular and work quite well but keep in mind that as long as there is a reason for the flies to be coming to your place no control can keep up with the unlimited supply of flies out there.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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