Prediction models of grub population dynamics in wheat lands of South Shanxi Province

In order to correctly predict the grub population dynamics for a timely control, we investigated and analyzed grub genesis regulation in first-cropping and continuous-cropping wheat fields by chessboarol sampling method using 1982～2002 data collected in the wheat lands of South Shanxi Province. Furthermore, the influence of weather factors on grub population dynamics for different cropping systems was investigated and regression equations established by the adoption of multi-analysis method. Four factors including grub original density (X₁), August rainfall (X₂), rainfall in the last 10 days of September (X₃) and the 5 cm depth soil temperature in last 10 days of September (X₄) were selected and their correlations with infection degree of grub genesis (Y) determined. Based on path-analysis, the most important factor is grub original density, followed by weather factors. Regression equation for the first-cropping wheat field is Y=0.037 9+0.596 9X₁+0.001 9X₂-0.009 8X₃+0.046 0X₄ and that for the continuous-cropping wheat field is Y=1.765 5+0.634 8X₁-0.005 2X₂-0.003 7X₃-0.003 5X₄. For 1982～2006, the prediction rate of the models are 88% and 92% respectively. The results show that the prediction model is highly suitable for forecasting grub population dynamics.