House flies...

They seem to like my box... I hung paper up and snagged most. But not all are gone. Can a housefly be harmful to a plant? I heard they can pollinate plants.I have no males so no biggie. I just want to know if they can do any actual damage.

be sure you dont over water (mix in extra perlite to soil) to avoid blackfly. other than that you can get spiders (daddy long legs or something that cant bite u) or some other type of predator. if inside beware the NO-pest hot shot things have harmful chems in them and should only be used outside
get rid of the source (keep shit clean, no food/juice/beer out)of the flies and keep the screens all tight on your windows u keep open. this will avoid flys from repopulating
i bet u just have a lot of beer cans layin around