Abstract:Some natural occurring compounds, 5,7,4-trihydroxyflavone, quercetin, rutin, 5-methoxysalicylic acid and kojic acid, were selected to investigate the effects on the growth of Pieris rapae larvae. Dipping methods and ingestion methods were used and the results showed that the LC50 value of the chemicals against the tested larvae were 0.226 and 0.951 g/L at 72 hours after treatment with dipping methods for 5,7,4-trihydroxyflavone and quercetin, respectively, and 0.062 and 2.420 g/L with ingestion methods, respectively. All of the tested larvae couldnt pupated as 5,7,4-trihydroxyflavone beyond 0.200 g/L with ingestion methods, and the increased amount of body weight of the 5th instar larvae, which were dipped in the solution of 5,7,4-trihydroxyflavone, quercetin, rutin, 5-methoxysalicylic acid or kojic acid, were decreased obviously compared with the control. The vitro investigation showed that 5,7,4-trihydroxyflavone and quercetin could inhibit the activity of phenoloxidase from the larvae, and the IC50 were 25.65 and 43.94 mg/L, respectively.