Toxicity was determined for 15 acaricides against a laboratory strain of northern fowl mites, Ornithonyssus sylviarum (Canestrini and Fanzago). Adult females were exposed to residues on filter paper for 24 h. Three organophosphorous compounds (monocrotophos, cythioate, and famphur) were more toxic to the northern fowl mite than was carbaryl, the most commonly used pesticide in the poultry industry. The other tested compounds were less toxic to the mite than was carbaryl. Four of these, not used previously for northern fowl mite control, had low LC50's for northern fowl mites:aldicarb (0.46); pirimiphos-methyl (0.73); exo, exo-2,8-dichloro-4-thiatricyclo[3.2.1.0.]octane-4-oxide (AI3-63182) (0.87); and diazinon (2.48).
