Thermal resistance of different life stages of codling moth (Lepidoptera: Tortricidae)

Abstract

Phytosanitation regulations in several international markets require postharvest treatments to control codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in various commodities. Thermal treatments are gaining acceptance to replace chemical fumigation. Determining the most thermal-tolerant life stage is essential in the development of effective postharvest insect control protocols based on thermal energy. A heating block system was used to evaluate relative heat resistance of five different life stages of codling moth: white-ring eggs, black-head eggs, third-instar, fifth-instar, and diapausing larvae, at a heating rate of 15°C/min. The fifth-instar was the most heat-resistant life stage in the tested temperature range of 50–52°C except for diapausing larvae. Thermal death kinetic data of diapausing fifth-instar larvae were determined and also compared with the published TDT curve of non-diapausing larvae using the same heating block system. Both diapausing and non-diapausing larvae were dead after treatments at 50°C for 5 min and 52°C for 2 min. However, at the lower temperatures or shorter times, diapausing larvae had lower mortality than non-diapausing larvae.