Aaron's Expert Center


Summer Patch, Necrotic Ring Spot, and Brown Patch appear on lawns during times of stress. Generally these types of fungus will appear during the summer season. Snow Mold is a fungus that appears in the early spring. We have recommendations for both types of fungus.


Light Disease Damage

Light disease damage-High heat and traffic contribute to stressful conditions, making fungus more evident.



Moderate Damage

Moderate damage-Most of the time damage will fill in without long term damage. Organic fertilizer steps help suppress this level of damage. Note-lawn mowing has aggravated and spread fungus damage.


Severe Damage

Severe damage-This needs to be stopped with a fungicide. Organic fertilizer along with soil conditioning services, aeration and new, more disease tolerant cultivars (grass) will reduce future damage.


Summer Patch, Necrotic Ring Spot, and Brown Patch are root born diseases that make circles and frog eye shapes. Almost every lawn has had or does have these problems. These diseases are most evident in times of stress, like when it's dry and hot. Conditions such as excessive thatch, poor soil, sod installed over a poorly prepared site and poor cultural practices (mowing and watering) can give these fungus problems all they will need to do serious damage. In most cases, light to moderately damaged areas will recover with minimum long term damage. In severe cases, Fungicide treatments may be needed to stop the damage from getting any worse and rescue the rest of the lawn from infection. Treating light to moderately damaged lawns with a special organic fertilizer and aeration suppresses disease by balancing out soil problems naturally, and is a very cost effective and environmentally friendly long term option.


Summer Patch

Classic Summer Patch

Fungus Problems

There are many different types of fungus which grow in every lawn and it's unlikely that you could eliminate all disease causing fungi, and you wouldn't want to if you could. Many of the fungi that cause turf grass diseases are also important in nutrient cycling, especially in breakdown of thatch. However, if cultural conditions deteriorate these "beneficial" pathogens can cause serious problems.

Problematic Fungus: What is it?

There are several problematic types of fungus in our area. Some of the most common types include Summer Patch, Necrotic Ring Spot, and Brown patch. The damaged areas can appear as sunken spots of yellow turf that make patches or circles which are sometimes referred to as "frog eye". Damage can be aggravated with stress which can occur in many forms such as the wheels from the mower, which can leave what appear to be tracks of yellow turf behind a few days after it occurs.

Summer Patch

Summer Patch / Cut to Short


In the past Summer Patch and Necrotic Ring Spot were referred to as Fusarium Blight, however, recent research has led to the reclassification of these notorious types of lawn diseases.


Summer Patch:

Summer Patch is caused by the soil-borne fungus called Mangaporthe Poae. It is commonly associated with grasslands and appears mostly in Bluegrass and Fine Fescue grasses, but can show up in other types of cool season grasses as well. It is a warm weather root disease and grows best in temps between 80-85 degrees Fh and can occur in turf from mid-June through September and reappears during times of hot weather.

Tracks from mower due to fungus stress.

Tracks from mower due to fungus stress

Summer patch?s straw-brown splotches range from 6 inches to as much as 3 feet wide growing as the fungus infected areas age. Young roots may appear healthy during early stages of the disease, but will later show signs of discoloration and rot. Summer Patch moves from plant to plant creeping along roots and rhizomes and spreading at a rate of around 1 ? inches per week. Recently effected plants on the outer edge of the patch are often a distinct orange or bronze color and patches can even appear more bluish-green. The color is what makes summer patch hard to identify because most people don?t notice it until infected plants begin to die.


Fungus damage

Severe fungus damage needs to be stopped with a fungicide


Necrotic Ring Spot:

Necrotic Ring Spot is caused by the Leptosphaeria korrae fungus and it is a cool weather root disease. Symptoms are nearly identical to summer patch, however, in contrast to summer patch Necrotic Ring Spot kills roots in the late spring when soil temps reach 65 degrees and continues through the summer with symptoms appearing in late June and July.

Brown Patch:

Brown Patch is caused by fungus named Rhizactonia solani. It is active mostly in warm temperatures and symptoms begin to show under these conditions.

In Summary:

These "patch diseases" are similar in appearance and management and will likely return to the same areas of the lawn every year. Unless steps are taken to change the conditions in the lawn which lead to the propagation of these diseases they will rapidly spread. For even more detailed information please visit the University of Illinois Extension.




Fungus Prevention

Once damage has occurred these fungus problems are extremely difficult to control. Preventative maintenance and application of proper cultural practices are the best way to manage these types of lawn diseases.


Organic Fertilizer:

By looking at the picture above, the results speak for themselves. Both yards are fertilized with Granular Time-Release Fertilizer, However, the yard on the left is fertilized with Organic Granular Time-Release Fertilizer. Soil is more important to the overall health of your lawn than any other variable. It has been proven time and again that organics suppress fungus and stimulate healthy micro-organisms. By accelerating and stimulating microbial life (the life blood of rich soil), you can reduce thatch maintenance, increase drought tolerance, and insure better long term health. Getting your soil closer to the optimum organic state will make a lasting difference.

Healthy Soil Chart

Side by side: on the left results with an organic granular time-release fertilizer, on the right results with a standard granular time-release fertilizer



Proper Cultural Practices

The term "cultural practices" refers to the way you maintain your lawn. Your turf should be maintained in a vigorous but not in a over stimulated growing condition. Any factor that inhibits root growth will increase likelihood of turf disease.

Some key factors which can help maintain proper cultural conditions include:


Mowing to the proper height
(click to see our section on proper mowing)
Watering properly
(click to see our section on watering recd.)
Perform Regular Aeration
(click to see our section on Aeration)
Maintaining proper pH levels
(click to see our section on soil amendments)
Seeding instead of Sodding
(click to see our section on overseeding)
Preventative Fungicides
(click to see our section on Prev. Fungicide)
Use Organic Fertilizer
(click to see our section Organic Fertilizer)
Avoid liquid or quick release high nitrogen fertilizers!


Additional Information:

Maintaining Proper pH Levels:

Fungus Disease is most severe in soils with a pH above 6.5. To prevent this disease in turf, first conduct a soil test to find out what the pH is on your lawn. Then based on what is found in your soil test either sulfur (to lower the pH) or granular lime (to raise the pH) may be recommended to correct the pH of your soil.

Sod which has been recently (2-5 years) applied onto poorly prepared soil:

Improperly applied sod can lead to poor root penetration.(Examples: rocky soil, heavily compacted soil, clay based soil) Sod also comes with a heavy thatch layer which can hold moisture in and doesn't allow for proper air circulation.)



Snow Mold

Snow Mold appears on matted-down sections of the turf. Look closer and it looks like a fuzzy whitish substance on top of a matted down spot or section. It may have a pink cast around the edge if it's starting to develop Pink Snow Mold. As the lawn thaws, the crowns will be vulnerable coming out of dormancy. This can make severe damage if air circulation is poor, if the lawn was long going into dormancy, or has continued shade from trees and / or snow cover. Pink Snow Mold appears generally after 60 days and is the more severe damaging snow mold. You should lightly rake these areas to allow for air circulation, and to keep matted thatch from preventing grass growing through. Some thinning may be impossible to avoid because of winter dieback. A spring Core Aeration is a good option to expand the roots if thin areas are present. If you have matted down spots and you don't rake this out it may kill the grass.




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