Effect of Temperature Establishment Time on the Mortality of Epiphyas postvittana (Lepidoptera: Tortricidae) Larvae Exposed to a High-Temperature Controlled Atmosphere

Abstract

Mortality responses of 1st-, 3rd-, and 5th-instar Epiphyas postvittana (Walker) on apples to a controlled atmosphere (1% O2, 1%CO2) with 4 different times (5-12 h) to increase fruit surface temperature from 20°C (temperature during controlled atmosphere establishment) to 40°C (target temperature) were determined. Percentage mortality of all larval stages tested increased linearly on a complementary log-log scale with increase in treatment time. E. postvittana showed a general pattern of life-stage tolerance to treatment of 1st instar ≤3rd instar ≤ 5th instar. For all larval stages, mean lethal time (LT) estimates increased with increasing temperature establishment time. However, almost all insect mortality occurred within the period of temperature establishment. LT50s for all larval stages and LT99s for 1st instars increased less than the increase in temperature establishment time. Increasing the temperature establishment time increased the LT99 estimates of 3rd and 5th instars by an equivalent amount. No mortality estimate of any larval stage increased more than the increase in temperature establishment time.