What is Brown Patch?
Rhizoctonia Blight or the more commonly known name, Brown Patch, disease is a hot weather disease that can occur on all types of turf. However, it is most damaging to tall fescue, perennial ryegrass, creeping bentgrass and annual bluegrass. Kentucky bluegrass, Zoysiagrass and other species of grass can be occasionally injured and southern grasses tend to see injury later in the fall than the summer. Brown Patch often first appears as rough circular patches varying roughly from 1-5 feet in size. In the early morning dew, fine strands of grayish cobwebby fungal growth may be evident called mycelium. This quickly disappears as the dew dries. Individual leaves on the turf die back from the tip and can turn dark green then yellow as they wither and decay. Most importantly, Brown Patch is a soil based disease that can’t be eliminated from the soil. Proper management can limit the damage of the disease caused to the turf.
Conditions Favoring the TN Disease
Brown Patch is caused by infection of grass foliage and crowns by Rhizoctonia fungi. Rhizoctonia fungi often harmlessly colonize organic matter into thatch, however, during times of stressful conditions, Rhizoctonia can infect plants and cause disease. The conditions that favor Brown Patch development in cool season grasses occur when daytime temperatures are above 85 O
F and high relative humidity. A night temperature of 60 O
F in combination with evening showers or nighttime watering or relative humidity above 85% for more than 8 hours increases the chances of brown patch. In warm season grasses injury due to brown patch is most severe in humid weather with moderate temperatures (45-70 O
Rhizoctonia fungi will flourish during hot humid weather. Over watering, watering in the late afternoon, poor soil drainage, lack of air movement, thatch build up and shade on your lawn can create a favorable environment for Brown Patch. Mowing your lawn late in the evening, when the lawn is wet, or with a dull mower blade that frays the top of the leaf will also contribute to the severity of Brown Patch. Remember to keep your mower blade razor sharp and follow your Weed Man Mowing and Watering tips to help avoid Brown Patch.
Control Management of Brown Patch
Control applications of either granular or liquid product will do a good job in limiting the damage of Brown Patch. Preventive controls are good for up to 30 days and typically start at the first of May and continue through the summer. If Brown Patch is active in the grass it can be stopped with post control products. Applying the post disease control after Brown Patch activity is noticed will stop the spread, but the damage that has occurred will remain until the plant grows back or reseeding occurs. Lawns with a history of Brown Patch will continue to get the disease when conditions become right again; Usually around May or June. Weed Man Knoxville recommends preventative controls on a 25 to 28 day interval.