Mortality of Twospotted Spider Mite (Acari: Tetranychidae) after Exposure to Ethanol at Elevated Temperatures

Abstract

Mortality responses were determined for twospotted spider mite, Tetranychus urticae Koch, on apples to immersion in ethanol solutions at 20°C (nondiapausing and diapausing mites), and 30,40, and 45°C (diapausing mites only). At 20°C, nondiapausing T. urticae were more susceptible to ethanol immersion than the diapausing form. Increasing immersion times from 10 to 1,200 s significantly increased mite mortality for nondiapausing T. urticae but did not affect diapausing T. urticae. Increasing immersion temperatures for diapausing T. urticae from 20 to 40°C did not change the ethanol concentration required to achieve 99% (LC99) mortality. Raising the immersion temperature from 40 to 45°C only increased diapausing mite mortality at immersion times >800 s. Immersion of diapausing T. urticae for >600 s at 20°C in 70% ethanol achieved 99% mortality and was more effective than immersion at 30-45°C.