Selective Control of Tall Fescue in Kentucky Bluegrass with Chlorsulfuron¹

Abstract

Abstract Tall fescue ( Festuca arundinacea Schreb.) often occurs as a troublesome weed in Kentucky bluegrass ( Poa pratensis L.) turf. There is no labeled selective control for it, because of the physiological similarity of the two species. The objective of this study was to investigate the use of chlorsulfuron {2‐chloro‐ N ‐[(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl)aminocarbonyl]‐benzenesulfonamide} as a possible selective control of tall fescue in Kentucky bluegrass. Chlorsulfuron was applied in two greenhouse studies to ‘Baron’ Kentucky bluegrass and ‘Kentucky 31’ tall fescue in single application rates of 18, 35, 71, 141, 212, and 282 g (a.i.) ha −1 and split application rates of 18 + 18, 35 + 35, 71 + 71, 141 + 141, and 212 + 212 g a.i. ha −1 which were applied at a 2‐week interval. The experiment was conducted as a split‐plot with the two species as main plots and the 12 chlorsulfuron treatments as subplots in four replications. The tall fescue was damaged by a single application rate of 71 g ha −1 and a split application rate of 71 + 71 g ha −1 , and percentage control was observed to be 78 to 95% at application rates of 282 g ha −1 and above. Kentucky bluegrass showed a much greater tolerance to chlorsulfuron treatments, with little effect at the 282 g ha −1 single application rate and only minor damage at the 212 + 212 g ha −1 split application rate in both experiments. The results indicate that chlorsulfuron has the potential for use as a selective‐postemergence control of tall fescue in Kentucky bluegrass turf.