Toxicity of selected acaricides on Tetranychus urticae Koch (Tetranychidae: Acari) and Orius insidiosus Say (Hemiptera: Anthocoridae) life stages and predation studies with Orius insidiosus

Most management tactics for Tetranychus urticae (TSSM) rely upon applying acaricides. Multiple applications are required, which impact natural enemies. Growers will benefit from a more complete understanding of acaricide toxicity. My objectives were to determine: 1.) stage-specific direct and residual efficacy of three acaricides to TSSM; 2) direct and residual toxicity of these acaricides to O. insidiosus; 3) the functional response of O. insidiosus to mobile and egg stages of TSSM, in laboratory and greenhouse studies; 4) the abundance of O. insidiosus relative to TSSM densities in peanut.

Direct toxicity of three acaricides to TSSM was measured on peanut cuttings. All acaricides caused significant mortality, however; mortality did not differ among the acaricides. Residual toxicities against TSSM were not found to be toxic compared with untreated controls 24 and 72 hours after treatment. When acaricide toxicity to eggs was tested, the hatch rate for all treatments was significantly lower than the control hatch rate.

Direct toxicity of the acaricides was tested against O. insidiosus. Fenpropathrin and propargite caused 100% mortality and etoxazole resulted in mortality > 50%. Residual toxicity of acaricides to O. insidiosus adults varied. Fourteen days after treatment, fenpropathrin left residues highly toxic to O. insidiosus.

In laboratory studies, the functional response of O. insidiosus to TSSM eggs resulted in a Type III response whereas the functional response to adults was Type II. The data suggest either a Type II or linear response in greenhouse studies. A definitive conclusion cannot be drawn because of the sample size.