What is the difference between lawn and turf? A lawn, by definition, is an area of short, mown grass in a yard, garden, or park. Turf refers to grass and the layer of soil held together by its roots. If you speak to a horticulturist, they will use the term “turf” or “turfgrass” instead of lawn. In the dry, hot weather we’ve been having lately, most of our turfgrass species are stressed out and not looking too good- but there’s a big difference between stressed, dry grasses and diseased turf. This week, I wanted to share a few thoughts about turfgrass disease and what to look for.
First and foremost – continuous dry, hot weather can cause grasses to become stressed – and stressed plants are more susceptible to disease and other issues. Now is the time to raise your mowing height and hold off on any applications of pesticides or fertilizer. Most of our turfgrass diseases are going to be prominent in conditions of high temperatures, high humidity, over-fertilization, excess soil moisture, and extended leaf wetness. Some of these problems are environmental, but some are man-made. Be sure to follow proper fertilization recommendations of type, rate, and timing, and limit irrigation to first thing in the morning to ensure grass leaves have time to try out before the sun sets.
Brown patch is a fungal disease that can cause problems in turfgrass. Brown patch occurs primarily in cool-season species such as fescue, zoysia, centipede, and St. Augustine, but it can occur in bermudagrass as well. Brown patch appears in the turf as small, circular brown areas several inches in diameter, which quickly increase to 3-6’. These areas will often grow into each other, forming big irregular brown patches in the turf. This disease often develops during periods of humid, wet, overcast weather. Brown patch can be controlled with cultural changes such as mowing height, dethatching, and correct fertilization, and fungicides can be used as a last resort.
Dollar spot is another fungal disease that can occur in both warm and cool-season grasses. When dollar spot occurs, individual leaf blades will develop white lesions, ultimately creating small 3cm circular patches of yellow or brown colored grass in the lawn. Dollar spot can be controlled with cultural changes such as mowing and decreasing thatch. Fungicides alone will not control this disease.
Another one to look out for is fairy rings and slime molds. These are both fungal infections that occur in all grass species during warm, wet weather. Fairy rings create a circular band of darker-than-usual grass, with a center that may be dead or dying. During wet conditions, a ring of mushrooms might occur. To manage these areas, aerate the center of the rings, water thoroughly, and reduce thatch. Slime mold appears as a black, blue-grey, yellow, or tan substance on grass, and will often go away within 1-2 weeks on its own. To manage slime molds, you can rake or mow the mold out of the lawn.
Since it’s been so dry, I don’t anticipate getting many calls about lawn diseases. As you see, most of them are fungi, which require hot, wet weather to thrive. As we head through the growing season and into fall, be on the lookout- just in case. Questions? Call us at 706-359-3233 or uge3181@uga.edu.