瓜蚜(也叫棉蚜)繁殖力很强。有的农民问瓜蚜为什么越打越多,这是因为:一是治晚了。在夏季瓜蚜完成一代只需4～5天,所以,其数量增长的速度相当惊人的,如果虫量多了或者作物叶子卷了才打药,那就晚了。二是用药不当。比如拟菊酯类农药,开始使用效果很好,由于农民连续单独使用,很快便产生了抗药性,其效果越来越差,只好加大浓 Aphis gossypii (also known as cotton aphid) is very fertile. Some peasants ask why aphids hit more and more, this is because: First, rule late. Aphis gossypii in the summer to complete the generation of just 4 to 5 days, so the rate of its growth is quite alarming, if the amount of insect or crop leaves rolled up before playing drugs, it is too late. Second, improper medication. For example, the drugs of the pyrethroid pesticide are in good effect when they are started to be used. As peasants continue to use them alone, their drug resistance soon becomes worse and worse, and their effect is getting worse.