OXYGEN, CARBON-DIOXIDE, AND TEMPERATURE EFFECTS ON MORTALITY RESPONSES OF DIAPAUSING TETRANYCHUS-URTICAE (ACARI, TETRANYCHIDAE)

Diapausing adult twospotted spider mites, Tetranychus urticae Koch, we re exposed to various controlled atmosphere treatments at different te mperatures, to determine estimates of treatment times for 50% (LT(50)) and 99% (LT(99)) mortality when the O-2 concentration was reduced, gr eater reductions in lethal time estimates were achieved than when the CO2 concentration was increased. At 20 degrees C, an O-2 concentration of 0.4% combined with a CO2 concentration of 20.0% resulted in the lo west mean LT(99) (113 h). An increase in treatment temperature under t his atmosphere (0.4% O-2, 20.0% CO2) significantly decreased lethal ti me estimates. At 40 degrees C (the highest temperature tested) the mea n LT(99) was 15.5 h. Although a high temperature (40 degrees C) pretre atment advanced mortality under subsequent controlled atmosphere treat ment, the effect was small.