COMMODITY TREATMENT AND QUARANTINE ENTOMOLOGY Thermal Death Kinetics of Egg and Third Instar Mediterranean Fruit Fly (Diptera: Tephritidae) Y. GAZIT, 1 Y. ROSSLER, 1 S. WANG, 2 J. TANG, 2 AND S. LURIE 3 J. Econ. Entomol. 97(5): 1540Ð1546 (2004) ABSTRACT Two developmental stages of Ceratitis capitata (Wiedemann), 24-h-old eggs and third instars, 8 d after oviposition, were subjected to thermal exposures in a heating block system, at various temperatures of 46, 48, 50, and 52°C to determine the thermal death kinetics of the insects. At these temperatures, 100% mortality was achieved by exposure of 300 C. capitata larvae for 60, 15, 4, and 1 min, respectively. The 0.5 order kinetic model had the best Þt to the survival ratio for all the treatment temperatures, hence it was used for the prediction of the lethal times. The thermal death time (TDT) curves showed that the third instars were more heat-resistant than eggs, especially at the two low temperatures (46 and 48°C). Under temperatureÐtime combinations that did not result in complete kill,thethermalmortalityforeggswasalsosigniÞcantlyhigherthanthatforthirdinstars.Theactivation energy values calculated from the TDT curves were 490.6 and 551.9 kJ/mol, respectively, for thermal death of eggs and third instars. KEY WORDS Mediterranean fruit ßy, thermal death kinetics, heat treatment, heating block, radio frequency FRUIT FLY INFESTATION IS a major problem in the pro- duction,storage,marketing,andexportofcitrus.Many countriesrequireinspectioncertiÞcatesforabsenceof targeted live pests in a shipment after a preapproved postharvest “sanitation” treatment. Currently cold storage is the only treatment used commercially in Israel to disinfest citrus from Mediterranean fruit ßy, Ceratitis capitata (Wiedemann) (Diptera: Tephriti- dae). This treatment requires that the fruit be stored forupto16dat1.5°C.Unfortunately,thesafetymargin for fruit quality for this treatment is rather narrow, with many varieties developing chilling injury from the treatment (Wardowski et al. 1973, Schiffman- Nadel et al. 1975). Therefore, alternative heat treat- ments are of interest. Citrus is of subtropical origin and thus relatively tolerant to heat. The efÞcacy of heat as a method for disinfestingfreshcommoditiesfromfruitßieshasbeen demonstrated over the last decade by the success of forced hot air facilities for mangoes, grapefruits, and oranges in commercial applications (Mangan and Ingle 1992, 1994; Mangan et al. 1998). These treat- ments require that the fruit center reaches a target temperature within a given time and that this tem- perature is held for a required period to ensure a complete kill of targeted insects in fruit. Heating methods such as hot water immersion, forced hot air or vapor heat rely on heat conduction to transfer heat from the fruit surface to the fruit interior. The tem- perature gradient established inside the fruit is di- rectly inßuenced by fruit size, with larger fruit heating at a slower rate (Wang et al. 2001b). The lengthy conventional heating required to con- trol insect pests for large fruit such as citrus may result in thermal injury to the product (Lurie 1998). To minimize thermal damage to fruit, a more uniform and fast heating method by using electromagnetic energy at radio frequencies (RFs) may be used. RF heating is commonly used in commercial applications in the food, textile, and other industries and has indeed shown promises as a postharvest measure to control insect pests in selected commodities (Andreuccetti et al. 1994; Hallman and Sharp 1994; Nelson 1996; Tang et al. 2000; Wang et al. 2001a, 2002c). Information on the thermal resistance of different life stages and thermal death kinetics for targeted insects such as the Mediterranean fruit ßy is needed in developing effective thermal treatments for citrus. The temperatures used in the commercial heat treat- ments have been determined Þrst by testing in vitro the thermal exposure necessary to kill different stages of fruit ßies, then by testing of fruits infested with a sufÞcient population of fruit ßy to determine probit 9 values (99.9968% mortality) required by most coun- tries to meet quarantine security levels. Temperatures above 40°C are needed against larvae of a number of commercially important fruit ßy pests (Heard et al. 1991; Mangan and Ingle 1992, 1994; Nascimento et al. 1992;SharpandHallman1992;SharpandGould1994). 1 The Israel Cohen Institute for Biological Control, Citrus Market- ing Board of Israel, P.O. Box 80, Bet-Dagan 50250, Israel. 2 Department of Biological Systems Engineering, Washington State University, 213 L. J. Smith Hall, Pullman, WA 99164Ð6120. 3 Department of Postharvest Science, ARO, The Volcani Center, P.O. Box 6, Bet-Dagan 50250, Israel. 0022-0493/04/1540Ð1546$04.00/0  2004 Entomological Society of America