Question
After reading your response to the grass killer, I realized that I have been cutting my floratam too short and thus promoting weeds.  But I have a different problem, I have noticed large round brownish spots on my over trimmed and weedy lawn.  I think it might be a fungus.  I cut the watering back to once per week but the spots keep growing.  What do I do?

Answer
The symptoms you describe indicate a fungus, most likely brown patch. First though, let's eliminate irrigation and insect causes. Run the sprinkler zone long enough to determine that the area is adequately watered. Do a soap flush to make sure that harmful insects are not present in enough numbers to cause the problem. If these check out well, use a fungicide which has rhizoctonia (brown patch) and sclerotonia (dollar spot) on the label.