Acaricide Resistance in the Blue Tick, Boophilus decoloratus (Koch).—Part I

Abstract

Using laboratory tests described, the effectiveness of a number of insecticides on both larval and adult, fully engorged examples of the Blue Tick, Boophilus decoloratus (Koch), was determined. The results of tests using adult ticks were expressed as histograms of the percentage control exerted by varying concentrations of insecticides. The test using larvae was more sensitive and enabled results to be expressed as dose-response curves from which the LC50 could be accurately calculated. By comparing ticks from different localities in South Africa, resistance to a number of insecticides was demonstrated. Adult ticks from the farms Allandale and Ferndale in the East London district were three to four times more tolerant of sodium arsenite than were the sensitive ticks from Frankenwald farm near Johannesburg. Both larval and adult ticks from Ferndale and Allandale, when compared with Frankenwald ticks, were highly resistant to γ BHC, which conferred some cross-resistance to toxaphene, chlordane, dieldrin and aldrin. Ticks from Allandale, in addition to being resistant to sodium arsenite, BHC, toxaphene, chlordane, dieldrin and aldrin were highly resistant to DDT. DDT resistance conferred a cross-resistance to Dilan.The organo-phosphorus insecticides tested, malathion and diazinon, were equally effective against all ticks.