High temperature tolerance of the light brown apple moth, Epiphyas postvittana

The light brown apple moth (LBAM), Epiphyas postvittana, a leafroller native to southeastern Australia was discovered in California in 2006. The highly polyphagous nature of this pest adds to the importance of being able to predict the potential distribution of this invader across the North American continent. The spread of species from temperate origins with moderately warm summers, such as LBAM, can be limited by their ability to tolerate high temperature extremes. In California, generations of LBAM have been found to be strongly overlapping and the full range of life stages is present for most of the year. We therefore examined the high temperature tolerance for all LBAM life stages to determine lethal limits and most susceptible life stages. Our results showed that the mean lethal time leading to 50% mortality (LT50) ranged from 45 h - 187 h for the lowest temperature (32 °C), 1.2 h - 5.6 h for the highest temperature (41 °C) and 34 h - 68 h and 11 h - 21 h for the intermediate temperatures, 36C and 38C, respectively. At the three highest temperatures, LT50 increased with increasing larval instar while this trend was reversed for the lowest temperature (32 °C). Similarly, at the three highest temperature pupae had the highest LT50 values of all the life stages. This new information on LBAM high temperature tolerance will be invaluable for more accurately evaluating distribution limits for occurrence of any LBAM life stages.