Hey. We have some fungus growing on our lawn, and it has been there for a few years. We have overhanging trees (possible cause?)

Is there anything we can do to treat the fungus?

Please see attached photos...

http://img143.imageshack.us/my.php?i...19smallgw1.jpg

http://img143.imageshack.us/my.php?i...20smallke4.jpg

Any help is much appreciated :-)