|Hansen, James d|
Submitted to: Journal of Stored Products Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/30/2004
Publication Date: 10/1/2005
Citation: Yin, X., Wang, S., Tang, J., Hansen, J.D. 2005. Thermal resistance of fifth-instar Cydia pomonella (L.) (Lepidoptera:Tortricidae) as affected by pretreatment conditioning. Journal of Stored Products Research. 42(2006):75-85. Interpretive Summary: Deciduous tree fruits from the United States, such as apples and cherries, must currently undergo methyl bromide fumigation so that the fruits can be exported to Japan, a major market. Because of international agreements, the use of this fumigant may be discontinued. Postharvest thermal treatments have been proposed as a methyl bromide replacement for eliminating codling moths. During the growing season, ambient temperatures can be hot, greater than 100°F, which presumably affect codling moth larvae in the orchard. In this study, we examined heat resistance in fifth-instar codling moth larvae caused by pretreatment thermal exposures. Under laboratory conditions, heat resistance was induced in larvae so that treatment times needed to be significantly increased in order to show the same efficacy as with unpreconditioned larvae. However, preconditioning is lost after two hours when larvae are held at room temperatures. These results indicate that fruits should be held at moderate temperatures for several hours and not be subjected to thermal treatment directly from the field.
Technical Abstract: Codling moth (Cydia pomonella (L.)) is targeted for postharvest control by quarantine regulations in Japan and South Korea and by phytosanitation concerns in Europe. 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°C for 40, 120, 360 and 1080 min significantly increased the thermal resistance of C. pomonella. Pretreatment at 35°C for 360 min resulted in the highest heat resistance for fifth-instars. The minimum treatment times required to completely kill samples of 300 insects that went through thermal conditioning at 35°C for 6 h were 30, 7 and 3 min at 48, 50 and 52°C, respectively, as compared with 15, 5 and 2 min at those temperatures without pretreatment conditioning. After a pretreatment at 35°C for 360 min followed by a period of at least 2 h at 22°C, fifth-instar thermal resistance returned to the level that had existed before pretreatment conditioning.