SOIL INSECTICIDE AND PLACEMENT INFLUENCE CORN (ZEA-MAYS) TOLERANCE TO NICOSULFURON

Field experiments were conducted in 1991 and 1992 to evaluate corn tolerance to nicosulfuron following in-furrow or surface-band applications of seven soil-applied insecticides. The organophosphate insecticides evaluated included terbufos (15G and 20CR formulations), phorate, chlorpyrifos, fonofos, and DPX-43898, as well as the synthetic pyrethroid tefluthrin. Potential for a nicosulfuron/ insecticide interaction to injure corn was ranked as follows: terbufos 15G = phorate > terbufos 20CR > fonofos. Chlorpyrifos, DPX-43898, or tefluthrin followed by nicosulfuron caused no significant corn injury. Corn injury and yield reduction were greater in corn treated in-furrow compared with surface-band. Soil moisture at nicosulfuron application was more influential in causing corn injury and loss of yield than growth stage of corn at nicosulfuron application. Nomenclature: Chlorpyrifos O,O-diethyl-O-3,5,6-trichloro-2-pyridyl phosphorothioate; DPX-43898 O-O-diethyl O-(1,2,2,2-tetrachloro-ethyl)phosphorothioate; fonofos O-ethyl S-phenyl ethylphosphonodithioate; nicosulfuron, 2-[[[[(dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]-N, N-dimethyl-3-pyridine-carboxamide; phorate O,O-diethyl S-[(ethylthio)methyl]phosphorodithioate; tefluthrin, (2,3,5,6-tetrafluoro-4-methylphenyl)methyl-(1alpha, 3alpha)-(Z-(+/-)-3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethylcyclopropanecarboxylate; terbufos, S-[(tert-butylthio)methyl]-O,O-diethyl phosphorodithioate; corn, Zea mays L. 'Pioneer 3394.'