I moved into a new place which has a small 100 sq ft back patio which is infested with fleas. I cleaned up the dead leaves in the area and then sprayed raid flea killer. The next day they were still hoppin’. So I bought some DE and liberally dusted the whole area. It was obvious that it doesn’t kill them right away. How long should I wait until I go out back? I’m hoping that they will be gone but I know DE is not an automatic solution.