Insecticidal activity of three poisonous plant extracts against Mythimna separata

Laboratory studies were conducted to determine and compare the insecticidal activities of extracts from 3 poisonous plants in Tian Zhu alpine grassland.The results show that only the carbinol and ethanol extracts of Aconitum gymnandrum have determinate contact toxicity agaist armyworm with the LC50 values at 3.63,2.82 and 5.79 g/L.The carbinol extracts of A.gymnandrum,A.szechnyianum and Pedicularis scrophylariaceae exhibited strong insecticidal activity,their armyworm insecticidal LC50 values were 2.13,2.82 and 3.22 g/L respectively.The petroleum ether extracts of the three plant specises had weak insecticidal activity,such as petroleum ether extracts of A.szechnyianum and P.scrophylariaceae showed no significant stomach toxicity against armyworm.The extracts of the three different plant species which distilled from the 4 solvents exhibited difinite antifeedant activity to armyworm as well.The antifeedant activity of carbinol extracts from A.gymnandrum were obviously stronger than the others,and when the root extract of A.gymnandrum at 0.2 g/mL provided 97.6% inhibition of antifeedant rate in armyworm.The results also show that the antifeedant activities of petroleum ether extracts from the three poisonous plants were relatively weak.