We have lots of flies - it seems they have gotten up into the vinyl piece that covers the porch roof - it has zillions of tiny wholes for air. Well, flies have flown in and then laid eggs i believe - now we are dealing with the big flies that can't fit up there anymore. What can i do short of cutting a hole on each end of it and putting a bug bomb in there. It might solve it for this year, but then i'll probably have to do it every season. Is there something flies don't like that i can put up there?