Toxicity of Biorational Insectoacaricides to Cassava Red Spider Mite Tetranychus kanzawai Kishida (Acari: Tetranychidae) and its Phytoseiid Predator Amblyseius longispinosus Evans (Acari: Phtoseiidae)

Abstract

The minimum effective concentrations of biorational insectoacaricides such as abamectin and emamectin benzoate on the female adults of Tetranychus kanzawai Kishida (Acari: Tetranychidae) was investigated in vitro. Diluted concentrations for each biorational insectoacaricides were prepared by a factor of 10: 0.0001, 0.001, 0.01, 0.1, 1, 10, 100, and 1,000 mg of active ingredient/L of solution. The adulticidal bioassay revealed that 100 % mortality of the female adults of Tetranychus kanzawai could be achieved at concentrations of 100 mg/L and 0.1 mg/L of emamectin benzoate and abamectin, respectively. The residual toxicity test revealed that emamectin benzoate is highly persistent with a residual toxicity of 28 days compared to 1 mg/L abamectin in which its residual toxicity wears off after 24 hours of treatment. However, the 100 mg/L emamectin benzoate was highly toxic for the adults of Amblyseius longispinosus, whereas 1 mg/L abamectin showed no toxicity under laboratory conditions.