Enhanced Phytotoxicity of Bentazon with Organophosphate and Carbamate Insecticides

Abstract

The organophosphate insecticides, malathion [S-1,2-di (ethoxycarbonyl)ethylO, O-dimethyl phosphorodithioate], parathion (O, O-diethylO-4-nitrophenyl phosphorothioate) and diazinon (O,O-diethylO-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate) combined with bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide], caused severe injury to soybean [Glycine max(L.) Merr. ‘Corsoy′] and navy bean (Phaseolus vulgarisL. 'Seafarer′). Postemergence tank – mixture applications of bentazon with organophosphate or carbamate insecticides, or soil-applied organophosphate insecticides prior to bentazon treatments, did not interact with bentazon to injure corn (Zea maysL. ‘Great Lakes Hybrid 4122′). Technical grade malathion interacted with bentazon to the same extent as formulated malathion. Combination treatments of malathion with bentazon resulted in the same degree of injury whether they were applied as tank mixtures or split applications 48 h apart.