A temperature-based simulation model for the potato tuberworm, Phthorimaea operculella Zeller (Lepidoptera; gelechiidae)

The potato tuberworm, Phthorimaea operculella Zeller, is a serious pest of the potato, Solanum tuberosum L., in subtropical and tropical production systems around the world. Knowledge of the temperature-dependent population growth potential is crucial for understanding population dynamics and implementing pest control strategies in different agro-ecological zones. The development, mortality of immature life stages, and reproduction of P. operculella were studied at constant temperatures ranging from 10 to 32degreesC. The theoretical developmental thresholds were 11, 13.5, and 11.8degreesC, and required incubation times were 65.3,165.1, and 107.6 degree-days (DD) for the egg, larval, and pupal stages, respectively. The nonlinear shape of the temperature-development curve at low temperatures was well described by the modified four-parameter Sharpe & DeMichele model. The log-normal function was fitted to the normalized cumulative frequency distributions of developmental times for each life stage. Temperature effects on immature mortality were described by polynomial regressions. The optimal temperature for survival was within the range of 20-30degreesC. Temperature effects on adult senescence were described by the modified Sharpe & DeMichele model. A polynomial function was fitted to total fecundity and temperature. Fecundity was highest around 21degreesC. Age-related cumulative proportions of fecundity were well described by a Gamma function. Most eggs were laid within the first quarter of the female life span. The established functions were used to build a P. operculella population model, and life table parameters were simulated over a range of temperatures. Calculations gave good predictions when compared with published data. Populations increase within a temperature range of 10-35degreesC, with an optimum at 28-30degreesC.