COMPARATIVE MORTALITY RESPONSES OF 4 TORTRICID (LEPIDOPTERA) SPECIES TO A LOW OXYGEN-CONTROLLED ATMOSPHERE

In a controlled atmosphere of 0.4% 02, 5% CO2, previously found to rapidly kill the tortricid Epiphyas postvittana (Walker), the mortality responses of 3-d-old eggs and first, third, and fifth instars of three tortricid pests of New Zealand apples (two endemic species, Planotortrix octo Dugdale and Ctenopseustis obliquana [Walker], and an introduced species, Cydia pomonella [L.]), were determined at two different temperatures. At 20-degrees-C, all three species showed a pattern of susceptibility of the different stages to the atmosphere similar to that found for E. postvittana (i.e., in order of decreasing estimated time for 99% mortality [LT99]: fifth instars (including both diapausing and nondiapausing larvae of Cydia pomonella) > third instars greater-than-or-equal-to 3-d-old eggs greater-than-or-equal-to first instars. Responses of the four species showed a general trend of decreasing LT99s at 20-degrees-C in the following order: Cydia pomonella > E. postvittana almost-equal-to P. octo almost-equal-to Ctenopseustis obliquana. An increase in treatment temperature to 30-degrees-C resulted in significant decreases in LT99s for all stages of all three species by factors of between 1.8 and 9. The order of susceptibility of the four species at 30-degrees-C changed relative to that at 20-degrees-C, with smaller differences between Cydia pomonella and E. postvittana. Most noticeably, all stages of P. octo and Ctenopseustis obliquana had significantly lower LT99s than those of the corresponding stages of E. postvittana.