The current status of resistance to organophosphorus ixodicides by the blue tick, Boophilus Decoloratus (Koch) in the Republic of South Africa and Transkei.

In a four year survey 253 isolates of Boophilus decoloratus from the Republic of South Africa and Transkei were tested in the laboratory for their susceptibility to certain organophosphorus ixodicides. Fifty-seven of these isolates were susceptible to organophosphorus compounds, 88 isolates showed a range of susceptibility between that of the susceptible laboratory strain and a strain having a resistance greater than that for the Berlin type strain. A field trial confirmed degrees of resistance shown in the laboratory to the organophosphorus ixodicides benoxophos, chlorfenvinphos, dioxathion, dicrotophos, quintiofos and chlorfenvinphos/dioxathion.