Timely insecticide application against the summer generation (first field generation) of the plum curculio, Conotrachelus nenuphar Herbst, is critical in the production of peach and other stone fruits in the southeastern United States. In the absence of monitoring tools that are effective during midseason when the adults of this generation emerge, a temperature-based emergence model would be useful as an alternative decision aid. In this study, we determined rates of larval development (from oviposition to peak emergence of larvae) and pupal development (from larval emergence to peak emergence of adults) for two populations of C. nenuphar in constant temperatures ranging from ≈11–37°C, developed linear regression models to describe the relationships between developmental rate and temperature for both stages, and estimated degree-day requirements for completing development from these models. The lower threshold temperature was 11.1 and 8.7°C for larval and pupal development, respectively. The thermal time requirement from oviposition to peak emergence of larvae was 215.5 DD, and peak emergence of adults occurred 442.4 DD later. For model validation, rearing experiments were carried out with both populations in fluctuating temperatures in the greenhouse and outdoors. Observed degree-day requirements were not significantly different from model-predicted values for larval emergence in the greenhouse and for adult emergence in the greenhouse and outdoors. For larval emergence outdoors, the model overestimated time to peak emergence by ≈35 DD (2–3 calendar d), most likely because these trials were carried out during relatively cool conditions in which overestimation by a linear model would not be unexpected. Aspects related to further validation of the model and its use in orchard conditions are discussed.
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