Strobilurin Based Fungicide Programs Affect Rooting Characteristics and Plant Health Status of Creeping Bentgrass Putting Greens.

Previous research has indicated that improved turfgrass health may occur as a result of strobilurin fungicide applications during periods of summer stress. A multi-site experiment was conducted on ‘A4’ and ‘Southern dominant’ creeping bentgrass (Agrostis stolonifera) putting greens in Florence, SC and Strawberry Plains, TN respectively, to better understand the plant health benefits associated with strobilurin fungicides when integrated within a summer fungicide program. Fungicide programs contained 8 applications in Florence, SC and 5 applications in Strawberry Plains, TN. Fungicide program treatments consisted of different strobilurins being applied for the 2^nd and 5^th applications with other fungicide applications remaining similar among treatments. Ratings of visual turfgrass quality, color, normalized difference vegetation index (NDVI), ratio vegetation index (RVI), and digital image analysis (DIA) were collected at both locations throughout the trial period. Soil profiles were removed two weeks after the second strobilurin application to assess total root length and density using WinRhizo scanning software. Both locations, received applications of pyraclostrobin, azoxystrobin, and fluoxastrobin at rates of 0.55, 0.61, and 0.55 kg ha^-1, respectively. A program treatment containing trifloxystrobin was applied at 0.38 kg ha^-1 at the Strawberry Plains, TN location. Strobilurin fungicides were applied on 6 June and 18 July in Florence, SC and 15 June and 27 July in Strawberry Plains, TN during 2011. Pyraclostrobin treated plots at the Florence, SC location had significantly (P≤.05) greater NDVI and RVI compared to other strobilurin fungicide treatments on 5 rating dates in July and August, but this difference was not observed in Strawberry Plains, TN. Applications of strobilurin fungicides may provide a promotion of plant health during summer stress, but the observation of plant health effects may be dependent upon a number of factors that remain unknown.