http://www.youtube.com/watch?v=KeeOYGNlrsc&feature=player_embedded#!Here is a link to a you tube video from Dr. Dannergerer of the Ohio State University walking around home lawns and giving a great lesson of weeds and disease problems that you may be dealing with. I have seen a lot of the problems that he is talking about in the lawns and even golf course
I am sure he will answer some of your questions
Neil