杂草对人类的生产活动,特别是对农业生产造成的危害是多方面的。据联合国粮农组织估计,全世界每年因杂草和病虫害造成农作物减产损失达204亿美元,其中病害占27%,虫害占28%,线虫占3%,杂草则占42%,可见杂草的危害损失超过了病虫害的危害损失,因此,杂草的危害不能忽视。 甜菜地杂草的根系一般都比较发达,它能更多的吸收土壤中的水份和养价,因而降低甜菜产量。据法国调查,甜菜地杂草的发生对降低甜莱产量非常明显,如依甜菜地没有杂草其产量为100,而随着杂草数量的增加其甜菜产量递减(表1),当每一平方米 Weeds on the human production activities, especially on agricultural production caused by many hazards. According to the UN Food and Agriculture Organization, the annual loss of crops caused by weeds and pests in the world is estimated to be 20.4 billion U.S. dollars, of which 27% are diseases, 28% are pests, 3% are nematodes and 42% are weeds. Harm loss than pests and diseases harm the loss, therefore, weeds can not be ignored. The root system of beet weeds is generally well-developed, which absorbs more moisture in the soil and raise prices, thereby reducing beet yield. According to the French survey, the occurrence of weed in sugar beet is very obvious for reducing the yield of sweet and sour rice, for example, the yield of beet is 100 in the absence of weeds according to the beet and decreases as the weeds increase (Table 1) Square meter