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

The acaricide amitraz 1 , 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 fenthion 2 (2% a.i.) and prolate 3 (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” famphur 4 (13.2% a.i.), fenchlorphos 5 (4% a.i.), fenthion 6 (20% a.i.), and temephos 7 (20% a.i.) did not reduce tick numbers.