Acaricidal Efficacy of Three Organophosphates on Different Stages of Amblyomma variegatum

The study was conducted to compare the acaricidal effects of three organophosphorous pesticides, chlorfenvinphos, diazinon and coumaphos as Steladone , Asuntol and Diazintol , respectively. They were evaluated on different stages of Amblyomma variegatum (unfed nymphs, unfed adults and fed adults) using Shaw’s bioassay method. Three concentrations of each acaricides (within the recommendation) were tested on all the ticks’ stages. The highest mortality rate was observed in chlorfenvinphos treatments in all the stages and concentrations tested while diazinon produced the least effect. At the highest concentrations, all the acaricides produced high mortality rates but at the lowest concentration, diazinon was not effective. Generally, the acaricidal effects were concentration-dependent and the least mortality was recorded in the fed adult stage, depicting the possibility of blood and its constituent’s antagonistic interaction with the acaricide. The outcome of this study suggests that chlorfenvinphos and coumaphos could be used interchangeably because of the equivalence in their acaricidal effects. There is also the need for constant screening in order to ascertain Status.