Laboratory and field investigations with organophosphorus resistant Tetranychus urticae on strawberries

Laboratory tests using a slide dip technique confirmed that strains of Tetranychus urticae resistant to demeton-S-methyl and dimethoate had developed on strawberries in south Hampshire. These pesticides had been used very successfully for many years for the combined control of aphids and red spider mite. In small plot screening trials dicofol, phenisobromolate, chloropropylate, quinomethionate and dinobuton gave consistently good results. Binapacryl was very effective but caused damage to the plants. A number of other acaricides including formetanate and methiocarb were shown to be worth further investigation. Tetradifon, also used for some years on strawberries, gave variable results.