CREEPING BENTGRASS QUALITY FOLLOWING PREEMERGENCE AND POSTEMERGENCE HERBICIDE APPLICATIONS

Three field experiments were conducted to determine if several preemergence and postemergence herbicides were safe to apply to creeping bentgrass (Agrostis stolonifera L. 'Penncross') maintained at putting green height. When dithiopyr was applied at preemergence in late February or early March, the emulsifiable concentrate formulation (less-than-or-equal-to 1.7 kg.ha-1) and granular formulation (less-than-or-equal-to 1.1 kg.ha-1) did not reduce the quality or cover of creeping bentgrass. Applied at preemergence, bensulide plus oxadiazon at 6.7 + 1.7 kg.ha-1 and 13.4 + 3.4 kg.ha-1 reduced turfgrass quality for 2 to 3 weeks and 8 weeks after treatment, respectively. When MON 12051 and monosodium salt of methylarsonic acid (MSMA) (less-than-or-equal-to 0.14 and less-than-or-equal-to 2.2 kg.ha-1, respectively) were applied at postemergence to creeping bentgrass in early June, the reduction in turfgrass quality varied from slight to moderate for 1 to 2 weeks, but turfgrass fully recovered with no effect on turfgrass cover. Quinclorac applied at postemergence in early June at greater-than-or-equal-to 0.6 kg.ha-1 severely reduced creeping bentgrass quality and cover for greater-than-or-equal-to 8 weeks. Diclofop at 0.6 kg.ha-1 applied to creeping bentgrass in June, July, or August maintained consistently higher quality and cover ratings than when applied at greater-than-or-equal-to 1.1 kg.ha-1. Diclofop applied at 0.6 kg.ha-1 in June and repeated at the same rate in July reduced quality of creeping bentgrass less than when applied st 1.1 kg.ha-1 at any date. Chemical names used: O,O-bis (1-methylethyl) S-{2-[(phenylsulfonyl)amino]ethyl) phosphorodithioate (bensulide); (+/-)-2-[4-(2,4-dichlorophenoxy)phenoxylpropanoic acid (diclofop); SS-dimethyl-2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedicarbothtoate (dithiopyr); methyl-5-{[(4,6-dimethoxy-2-pyrimidinyl)amino] carbonylaminosulfonyl}-3-chloro-1-methyl-1-H-pyrazol-4-carboxylate (MON 12051); 3-[2,4-dicloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); 3,7-dicloro-8-quinolinecarboxylic acid (quindorac).