Acaricide resistance in the cattle tick, Amblyomma variegatum, in the coastal savanna zone of Ghana

Abstract

Field strains of the cattle tick, Amblyomma variegatum, collected from 10 herds scattered in the western part of the coastal savanna zone of Ghana, were tested for resistance to acaricides, according to the FAO Acaricide Test kit. Discriminating doses were obtained from tests with a reference susceptible strain of Boophilus microplus. The LC50 values, where possible, were derived from fitted lines for graphs of mortality rates versus acaricide concentration for the various herds. Tick larvae from all the herds were completely susceptible to cypermethrin (0.025, 0.05, 0.10, 0.20, 0.40, and 0.80 %) and flumethrin (0.003, 0.006, 0.012, 0.015, 0.03, 0.06, 0.12, 0.25, and 0.50 %). However, eight herds had significant proportions of tick larvae showing resistance to diazinon at 0.2 per cent concentration, while three herds showed resistance to 0.2 per cent dieldrin. At the discriminating dose of 0. 2 per cent coumaphos, none of the ticks from the herds tested showed resistance. The results indicate possible resistance of field strains of A. variegatum to organophosphates, toxaphene, and/or lindane. The implications of this finding are important, if tick control measures should be effective in the coastal savanna zone of Ghana.


Ghana Jnl agric Sci. Vol.32(2) 1999: 199-204