Yellow Patch and Disease
Development Te pathogen, Rhizoctonia cerealis, survives in the environment as thick-walled mycelial cells called bulbils, but also referred to as sclerotia. Tese bulbils remain dormant in plant debris, thatch, and soil during warm weather conditions, then, when colder conditions occur, the fungus grows and begins to infect turfgrass leaf tissues.
Yellow Patch and Cultural Control Cultural practices that may reduce the severity of yellow patch symptoms in turfgrass include applying a moderate amount of nitrogen fertilizer in the fall (i.e., avoid excess foliar growth in the fall), and reducing excess thatch and organic matter accumulation. Low temperatures, wet conditions, and also cloud cover can facilitate the occurrence of prolonged leaf wetness periods, which is a favorable environment for the development of yellow patch. Terefore, drying the turfgrass foliage (i.e., removing leaf wetness by mowing or other methods) can help reduce the appearance of yellow patch symptoms.
Figure 1. An example of yellow patch symptoms during the late fall season on creeping bentgrass grown for sod production.
Figure 3. An example of creeping bentgrass grown over plastic for sod production.
Sites with excessive soil moisture and poor drainage may be more susceptible to yellow patch. Creeping bentgrass sod grown over plastic (Figure 3) may be especially vulnerable to yellow patch. Terefore, consider a soil surfactant program in the fall to help facilitate improved infiltration and provide uniform and consistent soil moisture conditions.
Figure 2. Another example of yellow patch symptoms during the late fall season on creeping bentgrass grown for sod production. Te leaf tissues along the perimeter or outer ring of this individual patch were first a yellowish color then progressed to light brown, and surround a patch of blighted and partially-blighted leaves.
Terefore, yellow patch is typically observed during the cool or cold weather conditions of the fall, winter, and early spring (Figures 1 and 2). Te disease often occurs under snow cover, but does not require snow cover for disease symptoms to develop.
Mike Fidanza, PhD, is a professor of Plant and Soil Science at Pennsylvania State University, Berks Campus. Cale Bigelow, PhD, is a professor of Turfgrass Science and Ecology in the Department of Horticulture and Landscape Architecture at Purdue University in Indiana. They are teaming to provide a Rooted in Research article for each issue of Turf News. All photos are by Mike Fidanza, PhD.
TPI Turf News November/December 2024
Yellow Patch and Chemical Control Preventive fungicide applications in the fall can be used to control yellow patch. For control of disease symptoms that appear under snow cover, the fungicide should be applied prior to the first permanent snow cover in the fall or early winter. Applying fungicides after yellow patch symptoms appear in the late winter or early spring can halt the disease and prevent further turfgrass injury.
Refer to Tables 1, 2, and 3 as posted on the PSU turfgrass extension website at the link that follows for a list of fungicides available for consideration with Rhizoctonia diseases of turfgrass.
https://extension.psu.edu/turfgrass-diseases-cool-season-brown- patch-or-yellow-patch-causal-fungus-rhizoctonia-cerealis
Sources: • Burpee, L. 1980. Rhizoctonia cerealis causes yellow patch of turfgrass. Plant Disease 64:1114-1116. •Clarke, B.B., Vincelli, P., Koch, P., and Chou, M. 2024. Chemical control of turfgrass diseases 2024.
https://publications.ca.uky.edu/files/PPA1.pdf
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