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一、长期连续使用同种或同类农药。一个农户承包几亩地,买上一瓶农药就长期地、单纯地使用下去。这样,一种新农药用不了两、三年,害虫便很快地对该药产生了抗性。如80年代初开始使用拟除虫菊酯类农药时,防治棉蚜、棉铃虫使用浓度8000～10000倍,防效在95%以上。由于长期连续使用,致使多数害虫对拟除虫菊酯类农药产生了较高的抗性。据商河县1990年7月份试验,用2.5%溴氰菊酯800倍液防
First, long-term continuous use of the same or similar pesticides. A farmer contract a few acres, buy a bottle of pesticides on the long term, simply use it. In this way, a new pesticide can not use two or three years, the pests quickly gave rise to the drug resistance. Such as the early 80s when using pyrethroid pesticides, cotton aphids control, the use of cotton bollworm concentration of 8000 to 10000 times, the control effect of more than 95%. Due to long-term continuous use, most pests have higher resistance to pyrethroid pesticides. According to Shanghe County in July 1990 test, with 2.5% deltamethrin 800 times liquid defense