Screening For Bioactivities Of Plants Extracts Against Nilaparvata Lugens Stal And Pilot Study On Reaction Mechanisms

In this thesis, the effects on oviposition deterrent, repellent and contact poison of 98 extracts from 38 families 89 species of plants were evaluated against Nilaparvata lugens Stal. Bioactivities of the isolations and action mechanism of the active components were studied further by the laboratory bioassay. The main results were as follows:Effects on oviposition deterrent:â‘ When tested concentration reached 10g/L, most of crude extracts had some oviposition deterrent activities in different degree to N. lugens. There were 12 species of plants of which oviposition deterrent indices (ODI) in 24h had more than 50%. The extracts of branches and leaves of Gelsemium elegans, branches and leaves of Toona ciliata and Brucea javanica had the best effects with ODI in 24h reached 79.22%, 76.63% and 76.08% respectively.â‘¡The chloroform extracts of T. ciliata and G elegans had strongeractivities than others, which the ODI were 98.17% and 90.26% respectively. Thenext best were ethyl acetate extracts of T. ciliata and grease-dissolved part of B.javanica with ODI were 88.70% and 86% respectively. The ODI of otherisolations were all under 65%.â‘¢Effects on oviposition deterrent activities of the isolations of chloroform extracts of T. ciliata treated by silica gel column showed that the band 1st had...