Abstract: The toxicities of botanical acaricides scopoletin and bisdemethoxycurcumin (BDMC) were investigated for their acaricidal activity against female adults of the carmine spider mite, Tetranychus cinnabarinus, by slidedip bioassay at different temperatures in order to ascertain the temperature effect of scopoletin and BDMC. Both scopoletin and BDMC displayed a positive temperature coefficient at temperatures from 8 to 26℃ and a negative temperature coefficient at temperatures from 26 to 34℃. At 26℃, 48 h after treatment, scopoletin and BDMC showed the strongest acaricidal activity against T. cinnabarinus with the LC₅₀ values of 0.1884 and 0.3376 mg/mL, respectively. The mathematical models of the relationship between LC₅₀ (y) and temperature (x) were simulated: for scopoletin, y₁= 0.006x₁²-0.278x₁+3.403; for BDMC, y₂=0.007x₂²-0.354x₂+4.826. Based on the differential coefficients of above models, the optimal acaricidal activities of scopoletin and BDMC were obtained at 23.2 and 25.3℃, respectively, with the LC₅₀ values of 0.1828 and 0.3504mg/mL, respectively. It is so concluded that the toxicities of scopoletin and BDMC exhibit a positive temperature coefficient first and then exhibit a negative temperature coefficient with increasing temperature.

Key words: Tetranychus cinnabarinus, scopoletin, bisdemethoxycurcumin, toxicity, temperature effect