病虫害调查及损失估计 进行病虫害调查时,因为地区广阔,不可能每一个地方都调查,只能通过几个点取样检查来估计全面情况。因此,取样的原则就要具有足够的代表性,取样的具体方法,应根据当地自然环境、寄主植物及病虫本身的生物学特性综合考虑选择。一般田间调查分为棋盘式取样法和对角线取样法。棋盘式取样法的优点是所取的样本较均匀全面,缺点是取样前测量工作比较费工;对角线取样的优点是选点时手续较简单,但所取的样本不及棋盘式均匀。至于取样的单位,样本大小及个数等,要根据调查 Pest and disease surveys and loss estimates When conducting pest surveys, because of the vastness of the area it is impossible to investigate every single place and only through a few sampling points to assess the overall picture. Therefore, the sampling principle should be adequately represented. The specific sampling method should be based on the local natural environment, the host plant and the biological characteristics of pests and diseases themselves. General field survey is divided into checkerboard sampling method and diagonal sampling method. The advantage of the chessboard sampling method is that the samples taken are more uniform and comprehensive, and the disadvantage is that the measurement work before sampling is relatively laborious. The advantage of the diagonal sampling is that the procedure is simpler when selecting points, but the samples taken are not as uniform as the checkerboard. As for the sampling unit, sample size and number, etc., according to the survey