美国每年大量使用化学除草剂防除杂草。1970年使用量占农药总产量的60％,居第一位。每年大豆田用除草剂费约13亿美元(每英亩14美元)。杂草给农产品带来的损失,不亚于虫害。1970年以来美国开展生物防除杂草的研究工作,由昆虫、植病和杂草三方面专家参加。他们十分重视用植物病原物—真菌扑灭或防除杂草。因为真菌的特点:无处不在,高度专化 Every year, the United States extensively uses chemical herbicides to control weeds. In 1970, its usage accounted for 60% of the total pesticide output, ranking the first place. About $ 1.3 billion ($ 14 per acre) is spent annually on soya fields. Weeds to agricultural products losses, no less than pests. Since 1970, the United States has carried out research on the biological control of weeds and has participated in the field of insects, plant diseases and weeds. They attach great importance to using plant pathogens - fungi to fight or control weeds. Because of fungal features: everywhere, highly specialized