Not enough info - depends where you live precisely, what other treatments you've carried out, etc., and what you want to use to topdress it with.

people on this are only too glad to help you, but they do need to ask you questions, if you join the site you will be able to have a conversation about your problems and get very good advice from people who know what they are talking about, or you could be unlucky and get me ,lol

LMSO, Cliffo;-))