Pheromone/acaricide mixtures in the control of the tick Amblyomma hebraeum: effects of acaricides on attraction and attachment.

Unfed adults and nymphs of the bont tick Amblyomma hebraeum Koch are attracted to hosts on which fed males, emitting an aggregation-attachment pheromone (AAP), are attached. Pheromone/acaricide mixtures have the potential to selectively attract and kill these ticks. We have investigated the effects of three acaricides, amitraz (an amidine), flumethrin (a synthetic pyrethroid) and chlorfenvinphos (an organophosphate), combined with AAP, on the attraction and attachment of the unfed adults. Attraction, measured in field assays involving AAP and CO2, was not inhibited by any of the acaricides. Attachment was measured over 24 h on the ears of rabbits which had been treated with AAP and mixtures of AAP and the acaricides. None of the acaricides inhibited initial attachment. Flumethrin caused rapid and high mortality in attached and unattached ticks. Chlorfenvinphos caused little mortality in the first 24 h on the ears of the rabbits, but 75% of the exposed ticks died over the next 14 days while held in an incubator. Amitraz caused the ticks to detach after an initial period of attachment; there was little mortality in the detached ticks over the next two weeks and they could later be induced to re-attach to other rabbits. Flumethrin was considered to be the compound of choice for use in pheromone/acaricide mixtures.