Baseline susceptibility of Haemaphysalis longicornis to organophosphate, carbamate, and pyrethroid acaricides

The Asian longhorned tick, Haemaphysalis longicornis, continues to expand its range in North America, and synthetic acaricides are likely to play an increasing role in managing this species. Acaricide resistance is common in some tick species that infest livestock. However, baseline acaricide susceptibility has not previously been examined in this invasive tick.

We used a standard larval packet test to evaluate the susceptibility of the Asian longhorned tick to acaricides currently or formerly used in tick control: propoxur, carbaryl, bifenthrin, permethrin, and coumaphos. Discriminating concentrations were estimated at 6.5, 27.9, 988, 2242, and 808 ppm, respectively. The half-maximal lethal concentration (LC₅₀ ) values for propoxur, carbaryl, permethrin and coumaphos were compared with data available for other tick species and showed that H. longicornis was more susceptible to propoxur, carbaryl and coumaphos, and had a similar susceptibility to permethrin.

The results indicate that resistance to these acaricides is not currently a concern for H. longicornis in the United States. However, responsible integrated management and early detection of resistance can help ensure the long-term efficacy of products used for controlling this tick species. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.