Take-all root rot, a soil-borne fungal disease, has emerged as a destructive force against the roots of warm-season grasses, such as Bermuda grass, centipede grass, and zoysia grass. It can also be a huge problem in St. Augustine grass, found throughout the southern states. The disease has been found across Florida, as well as California, Alabama and Texas. Frequent, heavy rains in recent years have likely contributed to the spread of the disease.
With take-all root rot, the primary damage to the turf is a result of root infections. If rotting is minimal, the foliage may not be affected, but once aboveground symptoms are found, the disease can be hard to control. Once aboveground, the first signs of take-all root rot is a yellowing of the leaves. This usually appears in the spring and summer months. In the early stages of the disease, folding of the leaves along the midrib may occur. This is often followed by severe thinning of the turf in circular or irregular patches as the infected stolons die. In South Florida, where St. Augustine grass is prevalent year-round, recovery of take-all damaged turf often occurs during the winter months. However, when spring rains return, oftentimes so do the symptoms.
Unfortunately, specific control strategies for take-all root rot have not yet been developed. However, based on positive experiences with other patch diseases caused by the same fungus, control recommendations have been suggested. Because any stress placed on the turf can promote the disease, controlling take-all root rot should be more about turf grass management practices than chemical controls.
On several turf grasses, fertilizers that contain nitrate nitrogen increased the severity of diseases similar to take-all root rot, so it is recommended to avoid their use when possible. The use of slow-release fertilizers, or light monthly applications of fertilizers containing nitrogen, are recommended to maintain moderate turf growth and curb disease development. Other management practices can also help control take-all root rot, such as raising the cutting height for drought-stressed lawns, improving drainage in wet areas, and timely irrigation.
To date, using fungicides to treat take-all root rot has not been successful. Several fungicides for the control of take-all diseases caused by this fungus have been registered, however they have a high cost, limiting them only to preventive treatments on commercial and residential lawns previously damaged by the disease. Before applying any fungicide, you should core aerify or verticut the diseased areas, and then irrigate the fungicide into the soil with half an inch to an inch of water. Do not apply them immediately following a heavy rain.
Calling in professionals to handle this aspect of treatment is recommended. If you’ve noticed that your grass is not as green as it used to be, now is the time to act!