Insecticidal Activity of Pedicularis spicata Pall against Plutella xylostella

Contacting, antifeeding and inhibition of growth and development on 3th instar larvae of Plutella xylostella were determined. The results showed that ethanol extract possessed high effectiveness of contacting and antifeeding against 3th instar larvae of Plutella xylostella. The LC50 was 4.663 g/L by dipping method and the AFC50 of complete antifeeding activity were 8.238, 9.185 g/L in 24, 48 h, respectively. Ethanol extracts also had strong effect on the growth and development of Plutella xylostella. The treated larvae showed big reduction on body weight, pupation rate, adult emerging rate and relative growth rate comparing with control. The higher the concentration of the extracts was, the more severe the effect on the pest was. When treated with concentration of 50.00 g/L, growth inhibition rate was more than 100%, with pupation rate and adult emerging rate were 41.11%, 12.22%.