In three field experiments with weed-free plots, delaying the application of bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] reduced toxicity to cucumbers (Cucumis sativus L. ‘Poinsett 76′). Maximum injury and yield reduction were observed when bentazon was applied at the first leaf stage, whereas injury and yield reduction were slight when bentazon was applied at the fourth leaf stage. Increasing illuminance after application increased injury and tended to override the effect of leaf stage. In greenhouse studies, the slicing variety ‘Poinsett 76’ was more tolerant of bentazon than the pickling variety ‘Calypso’. The insecticide diazinon [O,O-diethyl-O-(2-isopropyl-6-methyl-4-pyrimidinyl)phosphorothioate] increased bentazon toxicity to cucumbers compared to toxicity caused by bentazon alone. Four other insecticides and two fungicides had no effect on phytotoxicity.
