Thanks for the question.

I suspect that we are dealing with a fungal disease here.  Three questions of you (I guess it is more than three questions):

1).  In past years and in 2021, how did your lawn look in the spring?  Say in late May to early June?

2).  In past years, when did you start to see these brown areas develop?  Spring, early summer, late summer?

3). Have you ever aerated your lawn?  Have you ever had the soil in your lawn tested?  

Thank you and we are looking forward to helping you!

Thanks for your response.

Things are now more in focus. Moles are not an issue. They strictly feed upon worms and insects in the ground. They can create mounds of dirt (probably what you are seeing on the perimeter) but normally this does not lead to grass browning. If it was some type of sun scorch, it would not necessarily appear every year as past seasons have not been as severe as 2021. My guess at this point is a fungal disease is the cause, more specifically what are collectively known as “patch diseases”. They are characterized by irregular shaped brown areas appearing during the latter part of the summer. Fortunately these diseases rarely kill grass roots but only affect the grass blades. When these blades go dormant during winter months, the growing fungi normally do not survive. However before this occurs and around this time (late August, early September), the fungi release millions of spores that end up on the soil and/or on the grass blades. These spores then germinate the following spring to produce new, growing fungi. These new fungi subsequently infect growing grass blades so that by late summer, these grass blades become brown. In short fungal lawn diseases are characterized by:

1). Relatively little brown grass in the spring before fungal spores germinate;

2). Grass browning becoming more obvious in mid to late-summer;

3). Spores that germinate in the spring may infect turf not previously infected so that the grass browning spreads;

4). Some previously infected grass may escape being infected again so that green areas may exist in previously brown areas

5). Depending upon climatic conditions, the shape of browned grass will change from season to season.

As for treatment, here are my suggestions:

1). Treating the brown areas in your yard now (late August 2021) with a fungicide will not serve any useful purpose. The growing fungi will largely be resistant to it. Fungicides are most effective when fungal spores are germinating and actively growing.

2). Rake the browned areas now to remove as much of the dead grass as possible. Discard this material. Hopefully this will reduce the number of fungal spores carried into 2022.

3). During the first week or two of September 2021, add a light layer of top soil (make sure this is specified on the bag) to the raked areas. Do NOT use soil that is labeled “black dirt”.

4). Seed these areas with grass seed that is approximately 50% bluegrass and approximately 50% of fescue. This fescue could be either tall or creeping.  Water, water, water. Do not add any fertilizer. New grass should be evident within two or so weeks.

5). In early spring 2022 (late April, early May), apply a fungicide to the previously seeded areas. Look for a fungicide that indicates it is effective against patch diseases such as Brown Patch. What you will be trying to achieve is the prevention of germination by fungal spores produced in 2021.

Basically the strategy is to control the spread of the fungus during the spring with fungicides and restoring the turf by reseeding in the fall.

These steps should reduce the browning in 2022. It will not completely eliminate it. To restore full turf in all the brown areas will require a repeating of the above suggestions for a few years. Take a look at the following, paying particular attention to the disease known as Brown Patch caused by the Rhizoctonia solani fungus. It is the most common fungal grass disease in the Metro Area.

https://www.jaredslawncare.com/identify-lawn-diseases

https://www.rainmasterlawn.com/blog/theres-fungus-among-us-understanding-summer-lawn-diseases

https://apps.extension.umn.edu/garden/diagnose/plant/turf/circular.html

https://www.scotts.com/en-us/library/lawn-disease-control/how-identify-and-control-brownpatch

https://hgic.clemson.edu/factsheet/brown-patch-large-patch-diseases-of-lawns/

https://extension.psu.edu/rhizoctonia

https://www.domyown.com/why-you-should-use-fungicides-in-your-yard-a-733.html

Two final points. Consider aerating your yard in fall 2022. Secondly, just to be sure that we are dealing with a fungal disease, you may want to submit a sample of the browned grass to the Plant Disease Clinic at the University of Minnesota immediately. Give them a call beforehand regarding exactly what to submit and what the cost will be:

https://pdc.umn.edu/

Good Luck. Please feel free to get back to us if you have any further questions.