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对于危害作物的某些害虫来说,化学药剂往往很少或没有效果。于是害虫不断繁殖,并损害更多的作物。侵袭树木的舞毒蛾便是这样的一种害虫。大约100年以前,作为改良蚕种试验的一部分,这种蛾子从欧洲被带到了美国。但蛾子从试验地逃跑了,由于缺乏天敌,不久便迅速繁衍遍布整个美国,演变成一场虫灾。从此以后,化学药剂对这种蛾子的控制失灵。科学家说,毒药对环境造成的危害比对舞毒蛾造成的危害更大。不过,大约10多年之前,美国科学家们研究发现了一种控制舞毒蛾的方法,那就是最早的“性引诱剂”的物理防虫法。
For some pests that endanger crops, chemicals often have little or no effect. As a result, pests continue to multiply and damage more crops. Gypsy moths that attack the trees are such pests. About 100 years ago, this moth was taken from Europe to the United States as part of a trial to improve silkworm eggs. However, the moth escaped from the experimental site and, due to the lack of natural enemies, soon multiplied throughout the United States and evolved into a pest. Since then, chemicals have failed to control this moth. Scientists say the harm done by poisons to the environment is more harmful than to gypsy moths. However, about a decade or so ago, U.S. scientists discovered a way to control gypsy moth, the earliest “physical attractant.”