Efficacy, Fruit Residues, and Soil Dissipation of the Herbicide Metolachlor in Processing Tomato

Abstract

Metolachlor was evaluated for annual grass and eastern black nightshade (Solarium ptycanthum Dun.) control in processing tomato (Lycopersicon esculentum Mill.). Metolachlor applied preplant incorporated provided excellent (> 88%) control of annual grasses and eastern black nightshade. The metolachlor, metribuzin plus trifluralin tank mix applied preplant and incorporated into the soil provided better annual grass and eastern black nightshade control than the metolachlor plus metribuzin tank mix in two of three years. Nonincorporated and posttransplant treatments of metolachlor provided good annual grass control but failed to control eastern black nightshade. Tomato yield in all herbicide treatments was similar to that from hand weeded controls. Metolachlor dissipated from the soil throughout the growing season so that at the time of harvest <10% of that applied was recovered. Metolachlor residues in the fruit were hydrolyzed to deacylated (CGA 37913) or hydrolyzed conjugated (CGA 49751) metolachlor metabolizes. Analyses of extracts from treated fruits were found to be less than the detection limit of 50 ppb in the whole fruit harvested from selected metolachlor treatments. Chemical names used: 2-chloro- N -(2-ethyl-6-methylphenyl)- N -(2-methoxy-1-methylethyl) acetamide (metolachlor); 2,6-dinitro- N,N -dipropyl-4-(trifluromethyl)benzenamine (trifluralin); 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-tlriazin-5(4H)-one (metribuzin); 2-(2-ethyl-6-methylphenyl)amino-1-propanol (CGA 37913); 4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morphol. inone (CGA 49751).