Fungicides for the Curative Control of Waitea Patch On a Chicago Poa Annua Golf Green.

Brown ring patch (Waitea circinata var. circinata) of creeping bentgrass was discovered and named by Japanese scientists in 2006.  Under similar environmental conditions a disease affecting Poa annua golf greens was known to exist in the United States but was called either Rhizoctonia yellow patch (R. cerealis) or Rhizoctonia zeae.  Since the mid-1980’s R. zeae had been reported affecting Poa annua putting surfaces in Illinois.  Waitea symptoms are narrow bright yellow rings that occur during wet periods from May to June.  The study assessed the distribution of Waitea patch in Chicago and evaluated curative fungicide treatments.  Three families of systemic fungicides (QoI, DMI, and carboximide) were compared for curative control of Waitea patch.  An untreated control, Daconil Ultrex (chlorothalonil), and liquid nitrogen fertilization by urea at 0.15 lb N per 1000 ft² served as comparisons. The fungicide study occurred at a golf green in play at Biltmore Country Club in N. Barrington, IL in 2008 and 2009.  At initial symptom development, treatments were applied with a CO₂-powered backpack sprayer with 8004 TeeJet flat fan nozzles at 40 psi in water equivalent to 2 gal/1000ft².  Individual plots were 4 ft x 6 ft and arranged in a randomized complete block design with 4 replications.  Waitea patch was quantified by estimating percent plot area damaged and counting the number of rings per plot.  Visual quality was also rated to estimate acceptable health and to quantify any phytotoxicity. Waitea was widely distributed throughout Metropolitan Chicago. The contact fungicide Daconil Ultrex did not control Waitea patch, whereas all systemic fungicides tested did.  Data is limited on the fertility effects of Waitea patch and nitrogen by urea did provide intermediate control.