European Corn Borer (Lepidoptera: Pyralidae) Development Time Model

Abstract

A nonlinear model for describing the larval development of the European corn borer, Ostrinia nubilalis (Hubner), was calibrated because previous work had revealed limitations of the degree-day model. The model proposed by Logan et al. in 1976 was used as a starting point. Experimental design was based on destructive sampling in order to record a large number of larvae, and on variable temperatures in order to fit the nonlinear model with few experiments and to avoid artifacts caused by constant temperatures. A calibration method was also proposed. The Logan model and the normal distributions describing the timing of the moult could be calibrated with the proposed method for temperatures ranging between 9 and 42°C. The model was validated under field conditions. Validation revealed that at least 1 environmental variable, probably maize phenology, that was not taken into account by the temperature model had a strong effect on the development rate. Leaving out the infestation where this effect was maximum (infestation during the early whorl stage), the model predicted the 2nd moult with a 48-h accuracy, and the last moult with an accuracy of better than 5 d. However, predictions were only half a day better than those obtained by the degree-day model. Nevertheless, this work helped to determine precisely the range of validity for the degree-day concept. Further investigations are along 2 directions: testing other mathematical formulations of the relationship between development rate and temperature to determine the possible limitations of the Logan formulation, and analyzing the influence of other environmental variables once the influence of temperature has been taken into account.