A field evaluation of the acaricidal effect on ticks was conducted in Chiba Prefecture in 2014. Eleven formulations of organophosphates and pyrethroids, including emulsifiable concentrate (EC), flowable (FL), dust and CO2 gas formulation, were evaluated simultaneously. These formulations were respectively applied to zones 2 m wide by 17–60 m long with dosages between 0.05–0.25 g AI/m2, which are the recommended dosages for cockroach control in buildings. The numbers of ticks collected by the dragging method with flannels were compared between pre- and post-treatment. The genus Haemaphysalis and Amblyomma were captured during the test period. All the formulations drastically suppressed the tick density on day 1. High reduction rates of more than 90% were observed until day 4 in all formulations, and persistence for at least for 31 days was recognized in fenitrothion EC, FL and fenthion dust. Phenothrin CO2 gas formulation that flows in the air with little residue in the soil or on foliage also yielded a long suppression effect at a dosage of 0.05 g AI/m2. Tick infestation from outside the test plot seemed to be feeble after the treatment. These results suggested that all the formulations achieved superior suppression effect on the ticks.
