MARC SPORLEDER1, JÜRGEN KROSCHEL2, AZIZ LAGNAOUI1
1International Potato Center (CIP), Integrated Pest Management, Peru
2University of Hohenheim, Institute of Plant Production and Agroecology in the Tropics and Subtropics, Germany
The potato tuber moth (PTM), Phthorimaea operculella ZELLER, is a serious pest of potatoes in tropical and subtropical regions. Knowledge of temperature-dependent population growth is crucial for understanding PTM population dynamics and implementing control strategies in different agro-ecological zones. We studied the development, mortality of immature life stages, and reproduction of PTM at constant temperatures in the range of 10-32°C. Theoretical developmental thresholds were 11, 13.5, and 11.8°C, and required incubation times were 65.3, 165.1, and 107.6 degree-days for the egg, larval, and pupal stages, respectively. Population parameters were best described by using the following models: nonlinear low-temperature development of immature life stages -- four"=parameter version of the SHARPE & DEMICHELE (1977) model; stage specific development frequency -- lognormal cumulative distribution function; mortality of immature life stages -- second"=order polynomial function; adult senescence -- SHARPE & DEMICHELE model; total fecundity -- polynomial function; age related cumulative proportions of fecundity -- cumulative gamma function. The established functions were used to develop a P. operculella population model using the rate"=summation approach. Life"=table parameters were simulated over a range of temperatures and calculated values gave good predictions when compared with published data. Population increase occurs within a temperature range of 10-35°C (optimum at 28-30°C).
Field research on population dynamics of PTM and life-cycle studies were conducted under various agro-ecological conditions in Peru, Egypt and Kenya. These life-table data obtained under fluctuating temperatures were used to validate the temperature-based simulation model which gave good predictions for each site. Possible uses of the model to predict critical field infestation periods and as a decision"=making tool in Integrated Pest Management of PTM are discussed.
Keywords: Life-table statistics, Phthorimaea operculella, population dynamics, potato pests, potato tuber moth, temperature-dependent development rate models