茜草乙醇提取物对小菜蛾的活性作用方式

Insecticidal Action of Rubia cordifolia L.against Plutella xylostella

研究了茜草乙醇提取物对小菜蛾的触杀、拒食和抑制生长作用。结果表明:茜草乙醇提取物对小菜蛾3龄幼虫具有较高的触杀和拒食活性,浸渍法处理对小菜蛾3龄幼虫72h的致死中浓度(LC50)为4.869g/L,24、48h的拒食中浓度(AFC50)分别为5.956、6.011g/L;乙醇提取物对小菜蛾的生长发育也有一定抑制作用,随施药剂量的增加,生长抑制率增大,化蛹率和羽化率降低,处理剂量为50.00g/L时,生长抑制率为98.96%,化蛹率为42.51%,羽化率仅为12.50%。

Contacting, antifeeding and inhibition of growth and development of Rubia cordifolia L. on 3th instar larvae of Plutella xylostella were determined. The results showed that ethanol extract possessed high contacting and antifeeding effects against 3th instar larvae of Plutella xylostella. The LCso of contacting action was 4.869 g/L by dipping method and the AFC50 of complete antifeeding activity were 5.965 and 6.011 g/L in 24 and 48 h, respectively. Ethanol extracts also displayed strong inhibition of growth and development on Plutella xylostella. Comparing with the controlled, the treated larvae showed big reduction on body weight, pupation rate, adult emerging rate and relative growth rate. 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 98.96%, with pupation rate and adult emerging rate were 42.51% and 12.50%.