THERMAL DEATH KINETICS AND HEAT TOLERANCE IN EARLY AND LATE 3RD INSTARS OF THE ORIENTAL FRUIT-FLY (DIPTERA, TEPHRITIDAE)

The kinetics of thermal death for early and late third instars of the oriental fruit fly Dacus dorsalis (Hendel) were determined at temperatures between 43 and 48-degrees-C and from 0 to 70 min using a hot water immersion technique. Both developmental stages exhibited nonlogarithmic death (survivorship) curves that were characterized by an initial lag in mortality followed by an increasing death rate with time at a given temperature. Based on Q10 values, popping (late) third instars appeared more resistant to heat than feeding (early) third instars. Arrhenius plots of larval death rates (k) indicated parallel slopes. The plots were different from Arrhenius plots of eggs and first instars reported in an earlier study. Comparison of the times necessary to achieve a predicted mortality using either thermal death rate analysis or probit analysis were similar to actual survivorship data at the high mortality level, suggesting that either could be used to estimate time-temperature-mortality for development of heat-based quarantine treatments. This information is discussed with respect to susceptibility of D. dorsalis larvae to heat and use of predictive models for disinfestation studies.