Sod Diseases

Necrotic Ring Spot

• Necrotic ring spot is a common disease in high-maintenance Kentucky bluegrass lawns. The disease typically strikes in the spring and fall. It appears first as rings of normal, straw- and red-colored blades of grass that can be up to 24 inches in diameter. Eventually the roots and crowns of the affected plant become covered with a black fungus. Once established, it's difficult to get rid of. It may come back each season for up to four years, according to North Dakota State University. Shallow roots encourage the disease. Aeration using core aerators or solid tine aerators will loosen the soil and help promote deep root growth. Keeping grass cut to at least 2.5 inches, using balanced nitrogen fertilizer and proper irrigation during drought periods will also help fight this disease.

Rhizoctonia Yellow Patch

• When new sod is laid on heavy soils or in lawns with heavy thatch and compacted soil, a fungus called Rhizoctonia cerealis can cause yellow path disease in the turf. It tends to infect Kentucky bluegrass as well. The disease shows up as wide yellow to reddish spots that may appear sunken. It looks similar to necrotic ring spot, but does not have the black strands of fungus visible on the plant. Too much watering can cause this problem, as can compacted soils. Reducing water and aerating compacted soil could help resolve the problem. Fungicide is not recommended and is only occasionally effective. The symptoms of this disease are generally short lived, according to Purdue University.

Rust

• Shady areas, closely cut grass and new sod are all places where rust fungus shows up on grass. This fungal disease causes the lawn to take on a yellow or orange hue and results in a reddish cloud of dust when mowed. Severe infections cause grass to turn yellow and die. It weakens the lawn and promotes the death of the grass over the winter. Control rust by maintaining good grass growth and adequate watering. Remove the lawn clippings with a bagging and mulching lawnmower when mowing. This will discourage development of the fungus.

Fairy Rings

• Fairy rings show up in sod and all types of turf grass in the spring and summer. The rings are dark green or brown and are virtually unlimited in size. These rings can extend up to 50 feet wide in some cases. The fungus responsible for the rings lives deep in the soil and can be identified quickly by the appearance of mushrooms -- the fungus' fruit. Aerating the soil, drenching it with fungicide, as well as frequent mowing to destroy mushrooms are ways to control this fungal disease.