Through seedling resistance determination,resistance of ten rice varieties to brown planthopper(BPH),Nilaparvata lugens(St.l),was studied in the green house.Among these rice varieties,special secondary compounds of 6 varieties were characterized by chromatography,and the relationship of the main substance peak in chromatography and the resistance level was analyzed.The variety Mudgo were indentified as highly resistant(HR),Jingxian89,Huahang8 and Shengbasimiao as resistant(R),Xiaolongzhan,XianxiaoZhan,Huahang1and Yuexiangzhan as moderately resistant(MR),Shuanggui feeling insect reaction and TN1 as high susceptible(HS) to BPH.The results in green house were confirmed by the population growth index(I) of BPH in the paddy field.I value of BPH population with TN1 and Yuexiangzhan was 28.079 and 6.422 9 respectively,showing an increasing trend of BPH;I value with resistant varieties Mudgo and Shengbasimiao was only 0.862 8 and 1.513 8,respectively.The resistant effects of the resistant varieties caused by natural enemy factors were far more powerful than those of the sensitive varieties.In addition,the content variations of secondary compounds in rice plants indicated that there was significant correlation between compound peak in chromatography and the resistance level.The fit linear regression equation is y=21.076 7-0.597 2x.Therefore,analyzing the secondary compounds by high-performance liquid chromatography(HPLC) could be used as a simple and fast way to identify rice resistance against BPH and predict the dynamics of BPH populations.

The results from systematical investigation in field indicated that the migration regularity of the population of rice planthoppers Nilaparvata lugens and Sogatella furcifera kept temporal consistency in different resistant rice varieties.The N.lugens populations were different between two sensitive rice growth stages before northward migration,and aggregated in boot stage at the end of June and migrated to mid-tillering stage in early and middle July,however the maximal population of southward migration only appeared in mid-tillering stage.The obvious regularity of habitat metastasis of S.furcifera population was not found.The results of grey correlative degree analysis showed that daily mean temperature and daily mean air pressure had the most significant influence on N.lugens population in eight meteorological factors,and the correlative degree values of the same day were 0.387 3 and 0.384 6 respectively,while those values of backward three days were 0.449 0 and 0.424 3 respectively.

By using field investigation method and biodiversity index,the effect of different ecological control methods on population of brown planthopper(BPH),the structure and changes of major natural enemies were evaluated.The results showed that released duck had significant effect against BPH population.It could decreased the number of nymph to 60.92%.The effect of trilogy on BPH was better than that of the extract from Mikania micrantha Kunth.The combination of different ecological control management had obvious effect on BPH population,but the joint control effect had a development out of direct proportion .The Shannon-Wiener Diversity index(H′) of spider and parasite were increased in a different degree in different ecological management fields and in common pesticide fields.It was concluded that different ecological management was beneficial to natural enemies,fully utilizing natural control effect.