Tim,

Thanks for your question.

Your pictures do seem to indicate necrotic ring spot. This is the most troublesome of lawn diseases, and, as you’ve learned, difficult to control.

I’ve attached links to several CSU Fact Sheets. The first, on lawn care, gives some good overall recommendations for a healthy lawn.

The second addresses the necrotic ring spot directly.

As you’ll see, Kentucky blue grass is the hardest hit of all lawn grasses by necrotic ring spot. There are disease resistant bluegrass varieties you could overseed with. Also, perennial rye grass is immune to ring spot.

You mentioned the anti-fungals you’ve applied. Applying too many of these, and at the wrong time, may have further stressed the area you’re treating.

Sulfur is recommended as a treatment, as noted in Fact Sheet 2.901.

Finally, a key point to remember is not to overwater the area. Be sure your sprinkler system is working properly and covering all the lawn. If you don’t have a sprinkler system, take care that you’re watering evenly and for the right amount of time.

Please review the Fact Sheets, and let us know if you have any further questions or concerns.

Lawn Care:

https://extension.colostate.edu/topic-areas/yard-garden/lawn-care-7-202/

Necrotic Ring Spot:

https://extension.colostate.edu/topic-areas/yard-garden/necrotic-ring-spot-of-kentucky-bluegrass-2-900/

Thanks,

Kathy