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防治指标是在一定条件下,某一时间阶段内,作物所能耐受的、不造成经济损失的、最大害虫群体数量。这时植保费用与治虫挽回损失大致相等。因此,在防治指标以前,一般不采取防治措施,以免得不偿失;同样,在达到防治指标以后,如果不采取措施,就要造成经济损失。 为了求得可靠的防治指标,要分别地区进行数年田间试验。研究害虫密度与为害程度的关系;为害程度与产值和产量的关系;为害程度与减产值的关系;防治措施所能抑制
Control indicators are under certain conditions, a period of time, the crops can tolerate, without causing economic losses, the largest number of pests. At this time, the cost of plant protection and insect pest control are roughly equal. Therefore, prior to the prevention and control of indicators, prevention and control measures are generally not taken so as to avoid loss of goodwill. Similarly, economic losses will be caused if no measures are taken after the prevention and control targets are reached. In order to find a reliable indicator of prevention and treatment, several field experiments should be carried out in different regions. Studying the relationship between pest density and damage degree, the relationship between damage degree and output value and yield, the relationship between damage degree and decreasing value,