A COMPUTER SIMULATION MODEL OF POPULATION DYNAMICS OF BROWN PLANTHOPPER, NILAPARVATA WGENS STÅL

Abstract A comprehensive computer model, based on the concept and analysis of the population life system, was developed to simulate effects of major environmental variables on the population dynamics of brown planthopper (BPH), Nilaparvata lugens Still. The basic frame of the model consists of a multiple column matrix, which was used to describe the stage overlapping phenomenon and the age-stage-structure of the BPH population, and a set of difference equations, which was employed to calculate the growth of individuals from one age-class and stage to the next in the BPH population. The life cycle of BPH was incremented in the model into 10 degree-days age classes and simulations were run with daily time steps. The model incorporates 1) temperature-dependent developmental rates or eggs, nymphs, and adults; 2) stage-specific survival rates obtained from the life table data of BPH; 3) immigration patterns and rates of macropterous adults; and 4) female fecundity. General validation of the model was established by comparisons between simulated and observed population densities for five years at three locations, which represent plain, hilly, and mountainous aresa in Fujian Province, using actual daily weather data and immigration patterns of macropterous adults for each year as model inputs. Simulation results from the model output were also compared by varying the model inputs within realistic limits in order to analyze the model behavior. We think that this model may serve as the framework for further studies on biology and ecology of BPH, and used to study various integrated BPH management strategies. Moreover, this model could be adapted to describe the population life systems of other insects with minor modification.