THE POPULATION PREDICTION MODEL OF THE PINE CATERPILLAR

The pine caterpillar D. punctatus is the most destructive pest of pine forests in China. It occurs in thirteen provinces and infects pine forests over large areas. In this paper, its population system has been studied and its structure model has been established by means of method of system analysis to summarize the achievements in scientific research and practical experience. Steps of modelling are as follows:1.Life cycle of the pine caterpillar being divided into five stages.2.Abstraction and analysis of factors affecting population dynamics of the pine caterpillar.3.Quantitative expression of factors affecting population dynamics of the pine caterpillar.4.Model being built of (A) Population time dynamics model of the pine caterpillar; (B) Population dispersal model.In order to predict the population dynamics through time and space, forests are divided into many grids (100m×100m). The coordinates of each grid are expressed by (i,j), including background conditions and variables in every grid respectively.Population time dynamics model and population dispersal model can be combined together and used to simulate and predict the variation in the distribution and abundance of pest population.The simulation results of the model coincide with the real occurrence laws of the pine caterpillar at Hungpu Experimental Forests in Qianshan County of Anhui Province.