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

Diapausing adult twospotted spider mites, Tetranychus urticae Koch, were exposed to various controlled atmosphere treatments at different temperatures, to determine estimates of treatment times for 50% (LT(50)) and 99% (LT(99)) mortality when the O-2 concentration was reduced, greater 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 lowest mean LT(99) (113 h). An increase in treatment temperature under this atmosphere (0.4% O-2, 20.0% CO2) significantly decreased lethal time estimates. At 40 degrees C (the highest temperature tested) the mean LT(99) was 15.5 h. Although a high temperature (40 degrees C) pretreatment advanced mortality under subsequent controlled atmosphere treatment, the effect was small.