Efficacy of Acifluorfen on Broadleaf Weeds. Times and Methods for Application

Abstract

In field tests, common cocklebur ( Xanthium pensylvanicum Wallr.) was controlled at the one- and two-leaf stages with 0.3 kg/ha acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid}. Four-leaf common cocklebur required 1.1 kg/ha for comparable control. Acifluorfen at 0.6 and 0.8 kg/ha controlled 96 and 90% of entireleaf morningglory [ Ipomoea hederacea (L.) Jacq. var. integriuscula ] atone- and two-leaf stages, respectively, but control was reduced as plants aged. Dark applications (2100 h) were more effective than those at sun-up (0600 h) or midday (1200 h) in control of hemp sesbania [ Sesbania exaltata (Raf.) Cory], pitted morningglory ( Ipomoea lacunosa L.), and smooth pigweed ( Amaranthus hybridus L.). Hour of application had no significant influence on control of common cocklebur or prickly sida ( Sida spinosa L.). An increase in surfactant (80% alkyl aryl polyoxyethylene glycols) concentration enhanced acifluorfen control of entireleaf morningglory and Texas gourd [ Cucurbita texana (A.) Gray] at the 0.3-kg/ha rate applied 2 weeks after emergence. Soybean [ Glycine max (L.) Merr.] injury was increased with the 1.1-kg/ha rate when surfactant concentration was increased from 0.5 to 0.75%. Increasing the spray volume increased pitted morningglory control but decreased hemp sesbania control. In the growth chamber, better control of pitted morningglory and common cocklebur was obtained at high (35 C day, 26 C night) than at low temperatures (27 C day, 18 C night) when plants were treated 1 week after emergence.