The Rockdale Gardener

Gardening Posts From Rockdale Cooperative Extension

Warm Season Turfgrasses Suffering from Disease This Fall

The picture to the right shows zoysiagrass suffering from a patch disease Fall 2015. The image is classic Rhizoctonia Large Patch. The turf develops brown patches with purple borders as the fungus radiates out from the site of initial infection, consuming the turf roots and damaging the grass.

Rhizoctonia is fungus that infests warm season turf in the fall and spring if conditions are right.  Photo: by Barry Lee, Art-Scape Inc.

Rhizoctonia is fungus that infests warm season turf in the fall and spring if conditions are right.
Photo: by Barry Lee, Art-Scape Inc.

It is always best to try to avoid plant diseases by using IPM tactics. Integrated Pest Management techniques include using everything to control a pest reserving pesticides as a last resort. Growing a plant properly can avoid diseases.

UGA recommends the following to prevent or control Rhizoctonia:

 

• Use low to moderate amounts of nitrogen, moderate amounts of phosphorous and moderate to high amounts of potash.
• Avoid nitrogen applications when the disease is active.
• Increase the height of cut.
• Increase air circulation.
• Minimize the amount of shade.
• Irrigate turf early in the day.
• Improve the drainage of the turf.
• Reduce thatch.
• Remove dew from the turf early in the day (drag a hose over the turf).
• Warm season grasses — Fall preventative fungicide applications are BEST/MOST EFFECTIVE (Sept-Oct), with a follow-up SPRING application

UGA recommends the following fungicides for control of Rhizoctonia for homeowners: captan, mancozeb and thiophanate methyl. See the UGA Pest Management Handbook  for homeowners for more information.

The following synopsis of fall turf diseases, written by the Jones County Extension Service, is a good summation of turf issues this fall:

Take-all root rot is caused by a fungal infection of Gaeumannomyces graminis. The turfgrasses most commonly infected are St. Augustine, Bermuda, and Centipede. Favorable conditions for this disease are moist soils and a high pH (>6.5). Characteristics of this disease are large brown or bronze colored circular patches in the grass. Grasses infected with this disease will have dark brown roots. Some management practices that can help with this disease include using acidic fertilizers, improving the drainage of the turf, or applying a fungicide.

Brown Patch is caused by a fungal infection of rhizoctonia solani. Brown patch can infect all species of cool-season turfgrasses such as bent-grass, bluegrass, fescues, and rye grasses. Favorable conditions for this disease are warm temperatures with high levels of humidity and soil moisture. This disease is fairly active at cooler temperatures as well. Symptoms of this disease include rings or patches of damaged turf that can range from a few inches to several feet wide. Leaf spots may also be present along the edges of the patch. Some management practices include improving the drainage of the turf, reducing nitrogen applications, increasing the mowing height, or applying a fungicide.

Large Patch is caused by a fungal infection of rhizoctonia solani. Large patch occurs in the spring and fall as warm-season grasses are entering and exiting winter dormancy. Like Brown Patch, symptoms of this disease include rings or patches of damaged turf. In large patch, leaves along the edge of the patches may appear orange in color. Management practices are the same as those for Brown Patch. This is just a few examples of possible turfgrass diseases due to this unusually wet fall season.

DDDI – The Digital Distance Diagnostics Imaging system is invaluable to UGA County Agents in assisting homeowners and professionals with plant disease diagnosis. The attached image was sent via the sytem and this was the recommendation from our turf disease specialist:

“This is the result of having wet and 70 F weather. A fungicide application is highly dependent on the site. Wait until next spring before you see symptoms for fungicide application, unless (and I want to emphasize) unless in your area the grass is green and continue to be warm (above 70 degrees daytime and above 55 nighttime) temps. Otherwise wait until spring; fungicide and then fertilize. Because this site has now history of the disease; follow up next fall again before you see symptoms.”