Experiments were conducted in Virginia in 2000 and 2001 to investigate responses of winter wheat and diclofop-sensitive and -resistant Italian ryegrass to the experimental herbicide mixture AE F130060 03 and crop safener AE F107892 applied postemergence. AE F130060 03 at 15 or 18 g ai/ha with or without methylated seed oil controlled both diclofop-sensitive and -resistant Italian ryegrass 82 to 99% and reduced inflorescence emergence 59 to 98%. Although AE F130060 03 controlled existing Italian ryegrass 4 wk after any application, timing of application influenced late-season Italian ryegrass control and inflorescence emergence. Applications to two- to three-leaf Italian ryegrass resulted in greater emergence of Italian ryegrass after application than applications made to two- to three-tiller or four- to five-tiller Italian ryegrass. Wheat injury by AE F130060 03 was greater than injury from diclofop, but wheat appeared to fully recover; and yields from AE F130060 03–treated wheat were similar to yields of diclofop-treated wheat and at least 21% greater than yields from nontreated wheat. In greenhouse experiments, differential growth responses between diclofop-sensitive and -resistant Italian ryegrass occurred after AE F130060 03 application at normal (15 g ai/ha) and below-normal application rates. When rates were increased beyond normal application rates, growth responses were similar between diclofop-sensitive and -resistant Italian ryegrass.
Nomenclature: AE F130060 03 (8.3:1.7 mixture of AE F130060 00, proposed common name mesosulfuron-methyl, 2-[(4,6-dimethoxypyrimidin-2-yl carbamoyl)sulfamoyl]-4-methanesulfonamido-p-toluic acid, plus AE F115008 00, proposed common name iodosulfuron-methyl-sodium, 4-iodo-2-[3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)ureidosulfonyl]benzoic acid); AE F107892, proposed common name mefenpyr-diethyl, 1-(2,4-dichlorophenyl)-4,5-dihydro-5-methyl-1H-pyrazole-3,5-dicarboxylic acid; diclofop; Italian ryegrass, Lolium multiflorum Lam. LOLMU #3; winter wheat, Triticum aestivum. L. ‘Pioneer 2643’, ‘Pioneer 26R24’, ‘Pocohontas’.
Additional index words: Diclofop resistance, resistance management.
Abbreviations: ACCase, acetyl coenzyme A carboxylase; ALS, acetolactate synthase; MSO, methylated seed oil; POST, postemergence.