Abstract: Bioactivity and effect of rhodojaponin-Ⅲ on the Spodoptera litura cell (SL cell) and cell absorptivity of Na⁺, K⁺ and glucose were tested, and the effect on the cell amount of the 4th instar larvae of S. lituran was also studied. The resulted showed that when treated with 400 μg/mL and 200 μg/mL, the mortalities after 24 h treatment were 79.00% and 56.69%, respectively. The LC₅₀ to S. litura cell at 8, 16, 24 and 48 h after treatment were 240.09, 173.45, 113.56 and 73.40 mg/mL, respectively. Treated with rhodojaponin-Ⅲ, S. litura cells started to absorb Na⁺ and K⁺ rapidly in no less than 10 min, and 30 min later the absorbability wore off ; S. litura cells started to absorb glucose rapidly within 3 days, and in 4－5 days S. litura cells almost stopped uptaking glucose. Treated by leaf disc and injecting, the cell amount of the 4th instar larvae of S. litura receded observably, and recovered gradually as the treatment time extended.

Key words: Spodoptera litura, rhodojaponin-Ⅲ, bioactivity