Simulation Analysis of Brown Planthopper (Nilaparvata lugens) Population Dynamics on Rice in the Philippines

Abstract

(1) A simulation model of brown planthopper (Nilaparvata lugens Stal.) on rice was constructed using intensive field observations, made over a 5-year period in the Philippines, together with data obtained from the literature. The initial purpose is to simulate observed population changes, in order to understand the essential factors controlling the population dynamics of this pest. (2) Since the simulation model will be used subsequently to investigate the effects of management and climate on brown planthopper populations, a descriptive analysis of the rice agroecosystem has been the first step in the modelling process. Key components incorporated into the simulation model included: the pattern of N. lugens macropter immigration; hopper (all species) population density and crop effects on N. lugens fecundity and survival; crop effects on N. lugens adult morph determination; N. lugens mortality due to three groups of predators and three groups of parasitoids; and the effects of other hoppers as alternative prey for the predators. (3) The model adequately simulates brown planthopper populations in data sets from plots which represent a 15-fold range in peak brown planthopper population density. However, to achieve this, estimates of the range of immigration rates between plots have to be increased from 4to 11-fold. (4) To develop the model a series of populations was simulated and discrepancies were identified by comparisons with observed populations. Four factors may be related to the discrepancy associated with immigration estimation: (a) inclusion of transient macropters in immigration estimate; (b) underestimation of predation, particularly at low prey densities, near boundaries and before crop canopy closure; (c) overestimation of immigrant fecundity and mating success at low densities before canopy closure; and (d) poor estimation of macropter emigration.