Seasonal Programs for Control of Turfgrass Diseases Paul Koch, Tom Huncosky, Sam Soper, Ben Van Ryzin, and Dr. Jim Kerns Department of Plant Pathology University of Wisconsin - Madison OBJECTIVE To determine the efficacy of fungicide spray programs for the control of turfgrass diseases and abiotic stresses throughout the summer. MATERIALS AND METHODS The study was conducted at the O.J. Noer Turfgrass Research and Education Facility on a mixed stand of creeping bentgrass (Agrostis stolonifera) and annual bluegrass (Poa annua) maintained at a 0.100 inch cutting height. The individual plots measured 3 ft X 10 ft and were arranged in a randomized complete block design with four replications. Individual treatments were applied at a nozzle pressure of 40 p.s.i using a CO2 pressurized boom sprayer equipped with two XR Teejet 8004 VS nozzles. All fungicides were agitated by hand and applied in the equivalent of 2 gallons of water per 1000ft2. Eleven different fungicide/plant growth regulator programs were initiated at various times and applied as the protocols prescribed. Number of dollar spot infection centers, percent brown patch, and turfgrass quality (1-9, 9 being excellent and 6 acceptable) were visually assessed and subjected to an analysis of variance and means were separated using the Waller-Duncan test (P = 0.05). Results of the disease severity/intensity and turfgrass quality ratings can be found in table 1 and 2, respectively. RESULTS AND DISCUSSION Disease pressure was very high on the Seasonal plot in 2010. Dollar spot was the primary disease for most of the season, though brown patch was prevalent in August. All treatments provided significant reductions in dollar spot severity compared with the non treated control in June and early July, but differences were not apparent on treatments 3, 4, and 8-10 by the August 2 rating date. Treatments 3 and 4 contained only early season treatments but still provided significant reductions in dollar spot compared to the non treated control through the July 9 rating date. Programs 6 and 11 provided the most effective dollar spot control throughout the entire season. All programs provided significant reductions in brown patch severity on the August 16 rating date compared to the non treated control, and all programs except for the early season programs (3 and 4) provided excellent brown patch control. Most programs provided acceptable turfgrass quality in June and early July, but deteriorated as disease pressure and stressful conditions intensified. On the July 20 rating date only programs 5 and 11 provided acceptable turfgrass quality, and only program 11 provided acceptable turfgrass quality by the August 16 th rating date.
Table 1. Mean number of dollar spot infection centers and brown patch severity per treatment at the O. J. Noer Turfgrass Research and Education Facility in Verona, WI in 2010. Treatment Rate Application Date Dollar Spot Severity a Brown Patch Severity b June 11 July 9 1 Non-treated control 152.0a 443.0a 320.5a 63.8a 2 Bayleton Flo Triton Flo Triton Flo Chipco 26GT 0.5 0.5 FL FL FL FL FL FL c 121.3cd 133.8c 1.3c 3 FL FL 15.3c 247.5b 276.0ab 25.0b 4 FL 112.8ab 280.0b 270.5ab 30.0b 5 2.0 FL FL FL FL FL FL FL FL FL FL May 10 Sep 20 Nov 15 Nov 15 0.5c 39.0d 79.3cd 0.0c
6 7 Proxy Primo Proxy Primo Curalan EG Curalan EG 5.0 5.0 FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL June 1 Sep 13 Oct 20 Oct 20 87.5b 215.3bc 56.0de 0.0c 3.0c 179.5bc 237.0b 2.5c
8 9 QP Fosetyl-AL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL 18.8c 230.5bc 284.3ab 3.8c 15.8c 224.8bc 295.8ab 3.8c
10 11 QP Myclobutanil AP Fosetyl-Al QP T NEX QP Myclobutanil Concert Renown Medallion Medallion Concert Renown 1.2 1.2 3.0 0.25 0.25 FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL June 1 June 14 July 12 July 12 July 26 July 26 Aug 9 3 10.0c 18bc 259.8ab 0.5c 5.0c 17.3d 13.5e 0.0c FL Sep 13 a Dollar spot was visually assessed as number of dollar spot infection centers per plot. Means followed by the same letter do not significantly differ (P=.05, Waller-Duncan). b Brown patch severity was visually assessed as percent disease. Means followed by the same letter do not significantly differ (P=.05, Waller-Duncan).
Table 2. Mean turf quality ratings per treatment at the O. J. Noer Turfgrass Research and Education Facility in Verona, WI in 2010. Treatment Rate Application Date Mean Turf Quality c June 11 July 20 1 Non-treated control e 3.0e 3.0e 1.8f 2 Bayleton Flo Triton Flo Triton Flo Chipco 26GT 0.5 0.5 FL FL FL FL FL FL 6.3ab 5.5bc 5.5b 4.8b 3 FL FL 5.3d 5.0c 4.3cd 3.3de 4 FL e d 3.8d 3.0e 5 2.0 FL FL FL FL FL FL FL FL FL FL May 10 Sep 20 Nov 15 Nov 15 6.5ab 7.5a 6.0ab 4.8b
6 7 Proxy Primo Proxy Primo Curalan EG Curalan EG 5.0 5.0 FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL June 1 Sep 13 Oct 20 Oct 20 5.0d d 4.8c 4.8b 6.5ab 5.0c c 3.8cd
8 9 QP Fosetyl-AL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL 6.8a 5.0c c 3.8cd 5.5cd 4.8cd 4.3cd 3.3de
10 11 QP Myclobutanil AP Fosetyl-Al QP T NEX QP Myclobutanil Concert Renown Medallion Medallion Concert Renown 1.2 1.2 3.0 0.25 0.25 FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL FL June 1 June 14 July 12 July 12 July 26 July 26 Aug 9 3 6.5ab 5.0c 4.8c 4.3bc 6.0bc 6.3b 6.5a 7.0a FL Sep 13 c Turfgrass quality was visually assessed on 1-9 scale, with 9 being excellent, 6 being acceptable, and 1 being bare soil. Means followed by the same letter do not significantly differ (P=.05, Waller-Duncan).