Hello Michael,

Fungus diseases in lawns are difficult to positively diagnose without lab tests. And once the humidity and temperature are favorable, the fungus spores that have overwintered in the soil can spread rapidly.

The photos you shared help confirm that it is likely a fungus, but there is not sufficient sharp detail in the closeup photo to diagnose the exact fungus ravaging your lawn. Just to make sure, have you dug up dead areas in the late summer and make sure you do not have grubs? There is a test for grub density in this article: https://www.canr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn

The recommendation to add nitrogen for some fungus pathogens is appropriate. Some fungus attacks when the grass is stressed, and some added nutrition can help fend off the pathogen. Fungicides are generally the defense against fungal infections, but there are limitations with them as well: Fungicide effectiveness is fungus strain dependent. By the time you see the damage it is essentially too late to treat with a fungicide. The damage has occurred in the weeks to a month preceding. Even when the appropriate fungicide is applied at the appropriate time, they are not 100% effective.

So what do you do? First, if you haven’t gotten one, get a soil test to understand what you should be doing culturally for lawn growth. Details on MSU soil testing can be found at: https://www.canr.msu.edu/news/soil-testing-returns-through-msu-extension

Second, once the annual fungus bloom occurs, take a sample at a margin so that you have the dead grass, the dying margin and good grass all in the sample. Send this sample to the MSU Diagnostic lab to have the type of grass and the type of fungus identified. The services and cost structure for MSU Diagnostic Services can be found at:

https://www.canr.msu.edu/pestid/ Tips on how to take a good sample can be found at:

https://www.canr.msu.edu/pestid/submit-samples/

The results from the lab will positively identify the fungus, so you know what fungicides you should apply and when they should be applied. It will also identify the type of grass, because maybe you can grow a different cultivar that is less susceptible to your type of fungus. Then finally, the soil test will give you specifics about pH and nutrients so that you can optimize your cultural practices.

Once you get your results from the MSU Diagnostic Lab, feel free to answer with the results, so that we can suggest a treatment plan.