Comparative Toxicities of Selected Pesticides to Bulb Mite (Acari: Acaridae) and Twospotted Spider Mite (Acari: Tetranychidae)

The toxicities of 64 insecticides and acaricides belonging to several different chemical classes to the bulb mite, Rhizoglyphus echinopus (Fumouze and Robin), were examined with a contact-dip method. Results were compared with those obtained with many of the same compounds and the two spotted spider mite, Tetranychus urticae Koch, with the slide-dip method. Bulb mites generally were much more tolerant to the pesticides than were twospotted spider mites. Only 15 of 20 organophosphates and 6 of 8 carbamates had LC50’s <1,000 ppm for bulb mites after 72 h. Thus, the remaining organophosphates and carbamates and the 9 pyrethroids, 6 organochlorines, 4 formamidines, 14 specific acaricides, diflubenzuron, nicotine, and abamectin were inactive. Of the 49 compounds tested against twospotted spider mites, LC50’s <1,000 ppm after 48 h were obtained for all compounds except 6 organophosphates, 2 carbamates, endosulfan, and 2 specific acaricides. This marked difference in the pesticide susceptibility profile between these two herbivorous mite species suggests that major differences between these organisms may exist at the biochemical level.