SAFETY AND EFFICACY OF HALOSULFURON-METHYL FOR YELLOW NUTSEDGE TOPKILL IN COOL-SEASON TURF

Field studies were conducted in Kansas and Maryland to compare the saf ety and efficacy of halosulfuron-methyl (HM) and bentazon for topkill of yellow nutsedge (Cyperus esculentus L.), Kentucky bluegrass (Poa pr atensis L.) and creeping bentgrass (Agrostis palustris Huds.) treated with single (in Kansas) or sequential (in Maryland) HM (35 to 140 g . ha(-1)) or bentazon (1120 or 1680 g . ha(-1)) applications exhibited l ittle injury, and treated turf had acceptable quality in all studies. Bentazon caused an unacceptable reduction in perennial ryegrass (Loliu m perenne L.) quality at greater than or equal to 5 weeks after treatm ent in four of five tests. Perennial ryegrass quality declined linearl y with increasing HM rates (between 35 and 140 g . ha(-1)). In Marylan d, HM (greater than or equal to 70 g . ha(-1)) elicited unacceptable p erennial ryegrass quality for 2 or 3 weeks; however, in Kansas, qualit y was unacceptable for approximate to 1 week. In Kansas, yellow nutsed ge topkill by HM (70 kg . ha(-1)) ranged from 52% to 97%. A single HM application (35, 70, or 140 kg . ha(-1)) provided > 97% topkill in Mar yland. Yellow nutsedge topkill by bentazon (1680 g . ha(-1)) generally was inferior to that by HM (70 g . ha(-1)). Chemical names used: 3-(1 -methylethyl)-1H-2,1,3-benzothiadiazin-4 carbamoylsulfamoyl)-1-methylp yrazole-4-carboxylate (halosulfuron-methyl).