连作晚稻前期施药种类和时间对褐飞虱种群动态的影响

 田间试验研究了连晚前期施药种类和时间对褐飞虱种群动态的影响。结果表明施药后褐飞虱种群数量均有不同程度下降，但对褐飞虱主害代的控制作用与使用的农药种类和时间有密切的关系，而农药对褐飞虱的控制作用随种群的发展而下降。施药区褐飞虱种群增长倍数较对照区显著提高，其主要原因是农药对天敌尤其是对微蛛和黑肩绿盲蝽的杀伤作用。引起褐飞虱种群增长倍数提高的主要时期在四代成、若虫高峰期至五代卵高峰期，即施药后2～3周内。在各种供试药剂中，施用三唑磷的小区明显出现再增猖獗现象．根据以上结果，讨论了改善褐飞虱化学防治的途径。

The Effects of Timing and Insecticides Applied at Early Stage of Second Rice Cropping Season on Brown Planthopper,Nilaparvata lugens(Stal)Population Development

Field experiments on population development were carried out in northern Zhejiang,China.The results showed that brown planthopper BPH),Nilaparvata lugens(Stal),populations in various treatment plots were decreased in a range after insecticide application.The control efficacies for peak size,however,were closely related to the insecticides used and the timing,and the efficacies declined with population progressing.The population growth rates in sprayed plots were significantly higher than those in unsprayed plots,which were resulted from the side-effects of insecticides on natural enemies, especially the microspiders and mirids,and reduction of density-dependence effects. The main period causing increase of BPH population growth rate was from peak time of nymph plus adult of first generation after immigration,to peak time of egg of second generation after immigration,i.e.within 2 to 3 weeks after spraying.BPH resurgenced in triazophs treated plots. The possible approaches to improve chemical control of BPH were also discussed.