Lawn Problem Diagnosis Needed
Front and Back lawns were sodded in 2016 after home construction. No problems with uniformly healthy grass until early 2018 when large areas of back yard began to develop patches of dead grass. Watering and fertilizing were uniform across all areas. Front yard and parts of back yard remain healthy.
Lawn contractors and gardener agree with me that distressed areas need to be re-sodded, but we can't proceed without diagnosing and treating original problem, something we have been unable to do.
Denver County Colorado lawn
Diagnosing your lawn issue is difficult by photo but the damaged turf seems to be in arcs and circles which suggests that it may be the fungal disease Necrotic Ring Spot disease. I'm going to send you the fact sheet from CSU Extension on NRS for you to compare the information with your symptoms.
You also can take a sample into the Extension office for someone to look at it. The office is at 888 E. Iliff Ave. in Harvard Gulch Park (by Porter Hospital). If you do that, cut out a portion of the grass approximately 12" by 12" by 6-8" deep that shows both healthy and damaged turf. It s always a good idea to call the office before going down to make sure that someone is available. Their phone number is 720-913-5270.