杀虫剂诱使棉蚜再猖獗的研究

为指导棉蚜的综合防治，笔者对杀虫剂诱导棉蚜再猖獗的现象进行了研究，速灭杀丁，氧化乐果和久效磷对棉蚜田间施药试验结果表明：效果较好，但进入伏蚜发生期后，速灭杀丁处理区棉蚜种群上升极快，第3次施药手2000倍和4000倍的20％，速灭杀丁处理区棉虹种群数量分别是对照的9．05倍和7．22倍，氧化乐果施药区棉蚜密度也明显高于不 施药的对照区蚜虫密度，整个棉蚜发生阶段棉蚜的抗药性测定表明，随着用药次数增加，棉蚜对速灭杀丁抗性倍数增长迅速，第4次施药后LD56值是早春棉蚜的9．39倍。3种农药对七星瓢虫和异色标虫的毒性皆显著地对棉蚜的毒力，随着棉蚜抗药性增加，农药对瓢虫－蚜系统的破坏愈加严重，对3种农药处理后的棉蚜成，若蚜的生命表分析表明3种农药没有刺激种群增殖作用，因而可以认为速杰灭刹丁诱使棉蚜再猖獗的作用是由于棉蚜抗药性水平迅速提高和对棉田生态的破坏所致。

STUDY ON THE RESURGENCE CAUSED BY INSECTICIDES FOR COTTON APHID, APHIS GOSSYPII

Fenvalerate, omethoate and monocrotophos are the major pesticides for the chemical control of cotton aphid in Henan province. The experiment of application of these pesticides was done in cotton field in 1990, the result showed that plots by a successive three time spray with fenvalerate and four sprays with omethoate would induce the aphid population outbreak. The contrary was obtained in plots treated successively with monocrotophos. After the fourth time of using pesticide, population densities in two treatments with fenvalerate were 9.05 and 7.22 fold respectively compared to the control plots. The detection of resistance for the aphid indicated that as the times of applying insecticide increased, the level of resistance rose quickly, after the fourth time, the LD50 was 9.39 times that of early season before chemical control. Laboratory study found that pesticides were remarkably high toxic to nutural enemy such as Coceinella septempunctata and Leis axy-ridis. The analysis of life tables for adult and nymph treated respectively by the three pesticides pointed out that the rm value and other population parameters were not obviously different with the aphid untreated, there was no stimulating increase to the aphid fecundity.According to the result of experiment above, it is suggested that fenvalerate is unsuitable to control cotton aphid, the main reasons for inducing resurgence are the killing of natural enemies, destroying of cotton ecosystem, and making fast increase of insect pest resistance to insecticides.