Effects of pour-on organophosphate insecticides and a diamidide acaricide on the cattle tick, Haemaphysalis longicornis

Abstract The acaricide amitraz1, used at 0.025% a.i., caused a significant reduction in the number of Haemaphysalis longicornis female ticks for up to 10 days after its application to naturally infested unweaned calves. The “pour-on” compounds fenthion2 (2% a.i.) and prolate3 (10% a.i.) reduced the tick numbers on calves (but not to significant levels) to about half those seen on controls 3 days following their application (second treatment). There was no effect after 6 days (first treatment). Treatment of calves with the “pour-ons” famphur4 (13.2% a.i.), fenchlorphos5 (4% a.i.), fenthion6 (20% a.i.), and temephos7 (20% a.i.) did not reduce tick numbers.