Your lawn can get “sick” just like any other organism. For turfgrass, this usually comes in the form of fungus, rust, or mold / mildew (yes, like you get in your shower). Some turf types are more susceptible to diseases than others, and watering improperly will add to turf susceptibility. Once you notice disease issues, you need to act quickly to stop the spread of the disease in order to minimize damage to the turf.
Diseases common to the mid-south area:
Spring Dead Spot (SDS): Characterized by rings of dead grass varying from 6” to several feet in diameter, these rings will come back each season and can increase by several inches from year to year. The grass inside the rings is dead, will have a yellow/orange color and sink below the level of the healthy grass around it. SDS commonly affects bermuda and zoysia grasses. You will see it most often from mid-spring to early fall. The dead areas of grass will not recover, but once the fungus is treated, you can wait for the grass to grow back in, overseed or sod the affected areas.
Brown Patch: Characterized by brown, tan or yellow patches that range from a few inches to several feet in diameter. these patches are roughly circular. If the blades of grass are taller than 1” you will be able to see lesions or patches on the individual leaves. If less than 1” you may not be able to see lesions on the individual leaves, but you may see a black or dark grey ring (called a smoke ring) along the outside of the affected area. Brown Patch traditionally affects fescues and ryegrasses. You will typically see Brown Patch fungus mid-spring to early fall and it is usually worse during hot, humid weather. If you notice evidence of Brown Patch it is important that you contact your local extension office or lawn care professional for treatment protocol. With this fungus, it is especially important that you not apply nitrogen to the lawn as this will encourage the spread of the disease.
Dollar Spot: Characterized by small, silver dollar sized spots that are white to light tan in color. The leaves will have white to light tan lesions with reddish brown edges. Eventually these lesions will cause the leaf to die, causing the white patches. Dollar Spot can be an issue almost any time of year. If left untreated, these spots can merge into larger dead spots. Your local extension office or lawn care professional can develop a treatment plan to help minimize damage to your lawn.
Fairy Ring: Characterized by patches, rings or arcs initially less than one foot in diameter, this fungus can indirectly affect or kill the turfgrass. If left untreated, these rings will continue to grow year after year. Some rings have been noted at several hundred feet across in old turf stands. One defining characteristic of Fairy Ring is the relatively healthy grass inside the circle. This creates a hoola-hoop type ring. Fairy Ring can affect any turf time at any time of year. If the soil conditions are too wet, you may see mushrooms or puffballs along the affected area.
Rust: Characterized by small, yellow flecks that develop on the stems and leaves, these spots will develop into red/orange pustules that rupture to release a fine red to yellow powder of spores. If infected turf is disturbed, you will see clouds of spores. Rust primarily affects Zoysia, fescue and St. Augustine grasses. Rust is most often an issue during late spring and early fall. While proper watering and fertilization can help control rust, it is usually best to treat with a fungicide. Your local extension office or lawn care professional will have treatment recommendations.