Thermal resistance of fifth-instar Cydia pomonella (L.) (Lepidoptera: Tortricidae) as affected by pretreatment conditioning

Codling moth (Cydia pomonella (L.)) is targeted for postharvest control by quarantine regulations in Japan and South Korea and by phytosanitation concerns in Europe. Heat treatments may be used to control C. pomonella. But possible increase of heat resistance in insect pests, caused by pretreatment thermal conditions during harvest and storage periods, may compromise the efficacy of subsequent thermal treatments. A heating block system was used to determine the effect of pretreatment conditioning on the thermal resistance of the fifth-instar C. pomonella. Results showed that pretreatment conditioning at 35 1C for 40, 120, 360 or 1080min significantly increased the thermal resistance of C. pomonella. Among the above conditions 35 1C for 360min resulted in the highest heat resistance for fifth-instars. The minimum treatment times required to reach 100% mortality for 300 larvae that went through thermal conditioning at 35 1C for 360min were 30, 7 and 3min at 48, 50 and 52 1C, respectively, as compared with 15, 5 and 2min at those temperatures without pretreatment conditioning. After a pretreatment at 35 1C for 360min followed by a period of at least 120min at 22 1C, fifth-instar thermal resistance returned to the level that had existed before pretreatment conditioning. r 2005 Elsevier Ltd. All rights reserved.