One useful thing i have come across are the fly spray stickers in the shape of flowers etc.
My 4 kids never zip up the tent so we always get flies in there and since you shouldn't use sprays i stick one on the pole of their camp bunks and one on the frame of the pantry. Worked a treat! swept up quite a few dead flies.
I also stick one on the kitchen so i dont need to spray near the food.
I only use these for trips of a week or more as i'm not sure how cost effective they are.