Synergistic inhibitory effect of scopoletin and bisdemethoxycurcumin on Tetranychus cinnabarinus (Boisduval) (Acari: Tetranychidae).

The study aimed to investigate the synergistic activity of scopoletin and bisdemethoxycurcumin (BDMC) against the carmine spider mite Tetranychus cinnabarinus. The acaricidal activities of mixtures of scopoletin and BDMC against T. cinnabarinus female adults were measured via slide dipping and leaf disc dipping. A mathematical model was established by SPSS software. Bioassays for multiple effects including contact, ovicidal, cowpea root intake, repellency and oviposition inhibitory activity were carried out. The optimal mass ratio of the mixture of scopoletin and BDMC (at their respective LC(50)), the median lethal concentration (LC(50)) and the co-toxicity coefficient were 7:6, 0.19 mg/mL and 129, respectively. LC(50) values of contact activities of the mixture at optimal ratio against adults, nymphs, larvae, and eggs were 0.19, 0.18, 0.06, and 1.52 mg/mL, respectively. LC(50) values of cowpea root intake activity against adults and nymphs were 5.62 and 6.52 mg/mL, respectively. The highest repellent rates against adults and nymphs were 69.5% and 72.5%, respectively. The mixture of scopoletin and BDMC at the optimal mass ratio possessed strong acaricidal activity against T. cinnabarinus at various developmental stages.