A novel action of highly specific acaricide; bifenazate as a synergist for a GABA-gated chloride channel of Tetranychus urticae [Acari: Tetranychidae]

► We examined the bifenazate and its metabolite diazene on the GABA receptor. ► Both enhanced the GABA-mediated response, increasing the receptor affinity to GABA. ► These compounds are most likely allosteric modulator of Tetranychus GABAR. ► The contribution of GABAergic toxixity to acaricidal activity remains to be determined.