Abstract: In order to screen the environment friendly and highly effective insecticide of plant origin, we determined the contact toxicity of 52 extracts from 18 Chinese traditional herbal plants against the brown planthopper, Nilaparvata lugens Stål, by spray method and their stomach toxicity to Spodoptera exigua. The results showed that all the 52 extracts from the 18 Chinese traditional herbal plants separated with solvents of water, alcohol and petroleum ether had low activity to S. exigua, with the highest corrected mortality of only 33.33%. However, the extracts from Stemona sessilifolia Miq., Phellodendron chinense Schneid, Torreya grandis Fort, Gardenia jasminoides Ellis, Lappula myosotis Moench, and Aucklandia lappa Decne with solvents of alcohol or petroleum ether had high contact activity against the 3rd instar nymphs of N. lugens, with the corrected mortality of ≥80％ at 24 h after treatment at 0.8 g/mL, and the LC₅₀ values of their petroleum ether extracts were 0.0826, 0.0455, 0.0145, 0.0047, 0.0038, and 0.0033 g/mL, respectively. The bioassay results of systematic solvent extraction from the extracts showed that the insecticidal components of A. lappa and L. myosotis were predominantly present in the chloroform isolation, suggesting that their insecticidal activity components can dissolve in low-polar solvents. By tracking bioactivity of each fraction of the extract from L myosotis with column chromatography, we found that the Rf limit of the main insecticidal components in the plant was 0.5556-0.5926. This study lays the foundation for purification and confirmation of new insecticidal compounds from plants, including developing their application prospect and detecting novel insecticidal lead compounds.

Key words: Chinese traditional herbal plants, extract; Lappula myosotis, Aucklandia lappa, Nilaparvata lugens, Spodoptera exigua , insecticidal activity