We had a fly problem long before we had ducks, so our issue is unlikely to be improved by discouraging the flies from being around the duck pen. That’s why I chose the traps. But I may try the air fresheners instead of rebaiting the traps next time. They would definitely smell better than the traps. I do plan to hang them on my porches. My husband is allergic to most perfumes, so I’ll have to see how that goes. I think our neighbors may object, since our traps are probably catching most of their flies, too.