由于受环境的影响及自身生理活动,病虫害发生数量是不断变化的,在做药剂防治病虫试验中,需设不施药对照区,以对照区中虫口(或病指)的变动。来求药剂防治的真正效果。也可叫“校正防治效果”、“校正虫口减退率”,其计算公式是: Due to the impact of the environment and their own physiological activities, the number of pests and diseases is constantly changing, in doing pesticide pest control trials, the need to establish non-controlled application of pesticides to the control zone insect mouth (or disease index) changes. To seek the true effect of drug control. Can also be called “to correct the effect of prevention and control”, “correct the rate of population decline”, which is calculated as: