IPM Identification and Mangement Of Turfgrass Diseases

Author(s)

Brown Patch

Pathogen: Rhizoctonia solani
Hosts: Tall fescue, bentgrass, Kentucky bluegrass, perennial ryegrass, fine fescue

Symptoms and signs

Brown patch in tall fescue is first noticed as areas of the turf that turn purple to gray-green, resembling moisture stress. These areas quickly fade to light tan or brown as infected leaves dry out. The symptoms sometimes occur as discrete circular patches ranging from a few inches to several feet in diameter (Figure 1). More commonly, symptoms occur in large, diffuse areas (Figure 2).

Foliar symptoms in tall fescue are easy to see. Straw-colored foliar lesions with dark brown borders are apparent at the transition zone between healthy and diseased turf (Figure 3). Once the lesions have completely girdled the leaf sheath or leaf blade, the entire leaf quickly fades to tan or brown. Foliar symptoms are sometimes confused with those of dollar spot; however, dollar spot is rare on tall fescue.
Symptoms on bentgrass putting surfaces appear as copper-colored circles ranging in size from several inches to several feet in diameter (Figure 4). Foliar symptoms are not commonly observed on creeping bentgrass. During weather that is favorable to brown patch, mycelium (mass of fungal vegetative growth) can sometimes be seen in the early morning. It is found at the transition zone between healthy and affected turf and can be seen growing over and between the leaf blades (Figure 5). When the disease is active, there is often a dark gray border at the margin of the patch where mycelium can be detected. Hyphae (individual fungal strands) have a predominantly right-angled branching pattern in contrast to that of the dollar spot fungus, which is predominantly Y-shaped (Figure 6).

Conditions

Rhizoctonia solani survives in the thatch and soil as bulbils (resting structures). During favorable weather, hyphae from bulbils begin active growth and infect grass leaves. Brown patch develops rapidly when night temperatures exceed 70°F and duration of leaf wetness exceeds 10 hours. Brown patch can be severe following extended periods of hot (70–90°F), rainy, humid weather.

High levels of available nitrogen increase disease severity on both tall fescue and creeping bentgrass.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.