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Without actually seeing your lawn it is difficult to give you an accurate diagnosis of your problem.  There are several reasons that your lawn may have brown spots or rings.  The most common culprit is water.  If you have a sprinkler head that is blocked, missing, or broken it can cause some parts of your lawn to become brown.  A check of your sprinkler system can help you to identify if this is the problem.  You can find a once a month sprinkler system checklist at http://www.conservewater.utah.gov/OutdoorUse/MaintenanceCheck.htm.

Another reason you may be seeing brown rings in your lawn may be insect related.  Before applying any pesticides it is very important to identify what kind of insect it is.  The best way to diagnose an insect problem is to check the lawn.  Insects typically feed on the edges of the brown spots.  If you do find an insect but are unsure of what kind of insect it is the Utah Pests Webpage http://utahpests.usu.edu/  has a lot of information including pictures.  You can also bring a sample of the insect into the USU Extension Office located at 2001 S. State Street for identification.  Our office hours are Monday through Friday 8:00 am to 5:00 pm.

A third reason may be a fungal disease.  There are two different diseases that match your description.  The first is Necrotic Ring Spot.  This is a cool season disease that shows up March through May and September through November.  This particular disease is very common in 2 to 5 year old bluegrass lawns that have been established from sod.  It shows up as dead circles or arches of browning lawn that range in size from a few inches to a few feet that are surrounded by a patch of green lawn that gives a donut appearance.  The second disease is called Summer Patch.  It has very similar symptoms as Necrotic Ring Spot.  It becomes evident May through September.  Some recommendations in treatment for fungal diseases are:

1) Control thatch buildup with regular core aeration at least once a year. 
2) Water less frequently but to greater depth. The soil should be moistened 8 – 10 inches deep.
3) Remove layers of leaves from lawn during winter.

You can learn more about these turf diseases at http://utahpests.usu.edu/plantdiseases/htm/turf/turfdiseases.

To help provide you with a better diagnosis of what is happening in your lawn and a better treatment plan you can bring a sample into the USU Extension Office.  To take your sample, dig a 4- to 6-inch chunk of lawn (including the soil) on the margin of a brown spot.  Include a section with both living and dead turf.