Question
bluegrass lawn in northern missouri.  I have spots that are round and approximately 3 to 4 inches in diameter.  The blade is brown at the top but may be green at the bottom.  There is no banding to indicate that it is a fungus.  Suggestions would be most helpful   
Thanks
Les

Answer
Here is a list of lawn diseases in kentucky bluegrass:

http://www.american-lawns.com/problems/sick_lawns.html

http://www.realgreen.com/lawndisease1.htm

My guess based on time of year and grass type would be leaf spot.

Avoid excessive nitrogen fertilizers in spring. If you have not fertilized yet, apply a slow release fertilizer such as Ringer Lawnrestorer, Miloranite or Espoma Organic Lawn fertilizer now. then do not fertilize again until early fall. If you have fertilized already, then do not fertilize again.

If you water manually, water infrequently and deeply, such as once per week for 2 hours rather than 15 minutes daily. Lawn disease in spring is often due to excessive moisture (from a wet spring or overwatering) in combination with too much or too little fertilizer. therefore, if you have not fertilized, use a slow release version. If you have fertilized, do not fertilize again until fall.

Mow the lawn 2.5-3.5" tall and mow it frequently. Avoid growing the lawn excessively long before mowing, and do not mow it too close.