二、发生量的预测 影响害虫发生量的因子较多,许多害虫的大发生或再猖獗的原因又尚未完全弄清,因此,害虫发生量预测的难度较大。害虫发生量预测对于害虫防治工作十分重要。这里仅将常用的几种发生量的预测方法简要介绍如下。 (一)基数预测法 害虫的发生量一般与上一世代有效发生基数有密切关系,基数大,下一世代的发生量可能多,反之则少。依据基数的多寡来预测发生量,这是一种普遍采用的方法,尤其对一化性害虫和一年发生2～4代的害虫的第一、二代发生量的预测效果较好。如水稻三化螟、二化螟,棉花红铃虫、玉米螟等害虫,通过调查早春有效基数,可粗略地预测第一代的发 Second, the amount of the forecast There are many factors affecting the occurrence of pests, the occurrence of many pests or re-rampant reasons have not yet fully understood, therefore, pest occurrence is difficult to predict. Prediction of pest occurrence is very important for pest control. Here only a few of the commonly used methods of forecasting the amount of a brief introduction is as follows. (A) the base number forecasting method The pest occurrence is generally closely related to the effective generation base of the previous generation, the base number is large, the next generation may occur more, and vice versa. Predicting occurrences based on the number of bases is a commonly used method, especially for predicting the first and second generation occurrences of an obligatory pest and pests of 2-4 generations a year. Such as rice borer, Chilo suppressalis, cotton bollworm, corn borer and other pests, by investigating the effective base in early spring, can roughly predict the first generation of hair