8/7/2023 0 Comments Fertilome f stopThe first symptom of large patch most people notice is one or more circular, light green patches that may range in diameter from 2 inches to about 2 feet. A weak host, such as a warm-season turfgrass emerging from and entering winter dormancy, favors infection. High nitrogen fertility, especially in response to early fertilizer applications, increases turf susceptibility to the disease. At temperatures of 75 ☏ and above, and under low moisture conditions, the activity of the fungus decreases. Relatively cool temperatures (60 to 75 ☏) facilitate the disease while the cool nights and warm days typical of spring or fall may prolong it. Extended dew periods, rains, or excessive irrigation must be present because the disease is often worse in low, wet areas. While the fungus Rhizotonia solani is present all year in the soil, certain conditions are needed for disease to occur. This publication discusses the disease caused by Rhizoctonia solani on warm-season tufgrasses. As you might guess, the disease symptoms are different on cool-season grasses than on warm-season turfgrasses. The Rhizoctonia solani fungus also attacks cool-season turfgrasses, such as tall fescue, bentgrass, and ryegrass, but these plants are weakest in our summer heat, so it is a summer disease on them. This disease has been called many names, including “large patch,” “large brown patch,” “brown patch,” and “Rhizoctonia brown patch.” Augustinegrass, centipedegrass, bermudagrass, and zoysiagrass (warm-season turfgrasses) is most common in the spring and fall, and is usually not active during the summer, when the warm-season turfgrasses grow best. The fungus is actually a weak pathogen of warm-season turfgrasses, attacking them during emergence from or entering into winter dormancy, when they are at their weakest. This disease is caused by a fungus, Rhizoctonia solani, which also causes diseases of many agricultural and horticultural crops. The patches often occur at the same location year after year, usually in low areas or where dew or moisture stays for longer periods, such as shaded areas. In larger patches, the inside of the patch may begin to turn green again. The circular patches may continue to grow to 20 feet or more in diameter and may intersect other patches, creating complex patterns (Figure 1). It is characterized by circular patches with brown or smoky gray outer edges. Large patch is the most common lawn disease in Mississippi during the spring and fall. Augustinegrass, centipedegrass, bermudagrass, and zoysiagrass Quick symptomsīrown, round patches in the lawn leaf tips brown or red. Turf types affectedĪll warm-season turfgrasses, including St. WeatherĬool nights, warm days with rains or heavy dews. Spring and fall, when turf is emerging from or entering dormancy. Note circular patches (toward the top), and patches that have merged (toward bottom).
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