How can I get rid of the gray fungus that grows on my roof asphalt shingles? need a home remedy.?

all the homes in our neighborhood have a problem with roof fungus. there is a simple remedy for this -but- I can't rememb er it. help!How can I get rid of the gray fungus that grows on my roof asphalt shingles? need a home remedy.?
Zinc or copper. Usually, roofers will install a piece of zinc or copper flashing at the apex of the roof, which once rained upon, will leach out a small amount of either a zinc or cupric salt onto the rest of the roof. Compounds of either metal are generally toxic to plant life. You can do this yourself too, they sell this flashing at the home store.