Comparison of Three Herbicides For Selective Tall Fescue Control in Kentucky Bluegrass

Tall fescue (Festuca arundinacea Schreb.) can be an objectionable weed in Kentucky bluegrass (Poa pratensis L.). Field studies were conducted to determine safe and effective rates of chlorsulfuron [2‐chloro‐N‐{[(4‐methoxy‐6‐methyl‐l,3,5‐triazin‐2‐yl)amino]carbonyl}‐benzenesulfonamide], diclofop {(±)‐2‐[4‐(2,4‐dichlorophenoxy)phenoxy]propanoic acid), and metsulfuron [2‐([{[(4‐methoxy‐ 6‐methyl‐l,3,5‐triazin‐2‐yl}amino]carbonyl}amino]sulfonyl)benzoic acid] for selective tall fescue control in Kentucky bluegrass. Herbicides were field tested in either ‘Kenblue’ Kentucky bluegrass, grown on a Sassafrass sandy loam (fine‐loamy, siliceous, mesic Typic Hapludult), or an improved Kentucky bluegrass blend grown on a Chester silt loam (fine‐loamy, mixed mesic Typic Hapludult). Two applications of diclofo p reduced bluegrass cover and quality for extensive periods and generally provided inferior tall fescue control compared to chlorsulfuron or metsulfuron. Chlorsulfuron applied at 0.07 + 0.07 or 0.14 + 0.14 kg ha−1 did not reduce bluegrass cover at either site. Single applications of metsulfuron (0.07 or 0.14 kg ha−1) did not injure Kenblue; however, both rates injured the Kentucky bluegrass blend, and turf treated twice at the high rate required 1 yr for recovery. Single applications of chlorsulfuron (0.14 or 0.28 kg ha−1) or metsulfuron (0.07 or 0.14 kg ha−1) provided over 90% tall fescue control at the Kenblue site. Split applications of 0.07 + 0.07 or 0.14 + 0.14 kg ha−1 of either chlorsulfuron or metsulfuron provided over 90% control in the bluegrass blend. When compared to untreated turf, chlorsulfuron or split applications of metsulfuron applied in the fall, resulted in more bluegrass injury the following summer when turf was subjected to drought stress.