Synergism of diacylhydrazine insecticides with metyrapone and diethylmaleate

The two metabolic synergists, metyrapone (2‐methyl 1,2‐di‐3‐pyridyl‐1‐propanone) and diethylmaleate could increase the toxicity of the three most recent diacylhydrazines, representing a novel group of insect growth regulators (IGRs). These components are known as respective inhibitors of oxidative and glutathione S‐transferase enzymes. Larvicidal toxicity was tested in the laboratory by oral treatment against last‐instar larvae of the Colorado potato beetle Leptinotarsa decemlineata (Say) and of the beet armyworm Spodoptera exigua (Hübner). The obtained results should enable to improve the activity of tebufenozide, methoxyfenozide and halofenozide, and it may be used to suggest potential mechanisms for resistance against this novel group of IGRs, that is important to counteract cross‐resistance with other insecticide groups.