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自有农业以来,作物病害就一直威胁着农业生产,所以,不能把作物病害直接归咎于现代农业,然而,现代化的农业却加剧了作物病害的发展和蔓延。因此,总的来讲,目前的病害较之昔日严重,尤其是某些旨在最大限度增加短期效益的农业措施更加重了病虫的危害。这些措施包括在广阔的地域内使用较单一的作物品种、过量施用化肥和过量浇水(Carlson＆Main,1976)。另外,有些现行高产作物品种确实对病害很敏感,事先这些病害显得无关紧要,但是,一旦大规模地种植这些品种,那么,病害就迅速蔓延开来并造成损害。例如,在美国加利福尼亚州,白粉病(Erysiphe betae)和细菌性根系腐烂病(Erwinia spp.)都严重地损害了某些耐病毒病的甜菜品种,但这些病害未损害原始品种。
Crop diseases have been a threat to agricultural production since self-owned agriculture. Therefore, crop diseases can not be directly blamed on modern agriculture. However, modern agriculture has exacerbated the development and spread of crop diseases. Therefore, in general, the current diseases are worse than ever before, and in particular, certain agricultural measures aimed at maximizing short-term benefits add even more to pests and diseases. These include the use of simpler crop varieties, over-fertilization and watering over a wide area (Carlson & Main, 1976). In addition, some current high-yielding crop varieties are indeed susceptible to disease, which does not seem to matter in advance; however, once these are grown on a large scale, the disease rapidly spreads and causes damage. For example, in California, USA, Erysiphe betae and Erwinia spp. Both severely damage some resistant virus-resistant sugar beet varieties, but these are not damaging to the original variety.