Landscape and Irrigation is read by decision makers throughout the landscape and irrigation markets — including contractors, landscape architects, professional grounds managers, and irrigation and water mgmt companies and reaches the entire spetrum.
Issue link: http://read.dmtmag.com/i/465682
32 March 2015 Landscape and Irrigation www.landscapeirrigation.com Landscape and Turf MainTenance The Top Six Turfgrass Diseases Photo Provided by Syngenta The following are quick-reference facts regarding some of the most prevalent turfgrass diseases. Brown Patch Most common summer disease on cool-season grasses such as tall fescue, Kentucky bluegrass, and perennial ryegrass. Foliar disease that produces large, tan-colored lesions that ex- pand to blight circular patches of turf up to several feet in diam- eter. The brown patch pathogen, Rhizoctonia solani, active in the spring or early summer when nighttime temperatures are above 60 degrees Fahrenheit, but is most aggressive when high tem- peratures are above 90 degrees Fahrenheit combined with high humidity. Brown patch is most destructive in the transition zone where these conditions persist for months on end. Brown patch can be reduced with proper cultural practices, but preventive fungicide applications are often needed to prevent unacceptable damage, especially in the transition zone. For best results, initiate applications in the spring or early sum- mer when low temperatures consistently exceed 60 degrees Fahr- enheit and repeat on a 21- to 28-day interval depending on the product selected. Curative applications are effective in halting further disease ac- tivity, but may be slow because of the effect of high temperatures on the cool-season grasses. Large Patch Large patch is also caused by Rhizoctonia solani, but that is where the similarities end. Caused by a different strain of this pathogen specific to warm- season grasses. Centipedegrass, zoysiagrass, and St. Augustinegrass are highly susceptible to large patch. Large patch pathogen infects the basal portions of the turf plant. Tan or reddish-brown lesions evident on the leaf sheaths be- fore the entire tiller is killed. Over time, the disease expands to blight large circular patches of turf, sometimes 10 feet or more in diameter. Large patch attacks during fall, winter and spring when grow- ing slowly. Development largely weather driven, so there are few cultural practices that can limit the disease. Pathogen becomes active in the fall when soil temperatures de- cline below 60 degrees Fahrenheit, so this is the best time to begin a preventive fungicide program. Two applications in the fall and one application in the spring will provide excellent control in the majority of cases. Curative applications are generally ineffective because the turf is dormant or semi-dormant. Pythium BLIght Pythium blight is often considered a hot and wet weather disease, and that is true on cool-season grasses in warm-season turf. However, Pythium blight is caused by different species of Py- thium that infect during cool and wet weather in the fall and spring. Photo Provided by Syngenta Photo Provided by Syngenta