19世纪中期,一种称之为蓟的杂草传入美国后,由于缺乏天敌控制而迅速蔓延,现在数万公顷的土地上已长满了该杂草。蓟所到之处,就会将其他植物取而代之,使大量的土地失去了放牧的价值,它对马有毒,有时甚至是致命性的。在蓟的原产地,由于昆虫病原物的控制作用,它一直处于低量状态。为此,美国农业专家到其原产地调查了几种甲虫和蝇类,并在欧洲的设 After the introduction of a weed called thistle into the United States in the mid-1800s, it spread rapidly due to a lack of control of natural enemies, and the weeds were now grown on tens of thousands of hectares of land. Where thistles go, they replace other plants, leaving large areas of land with no value for grazing, poisonous and sometimes fatal to horses. In the country of origin of the thistle, it has been in a low volume due to the control of insect pathogens. To this end, U.S. agricultural experts investigated several beetles and flies to their place of origin and set up in Europe