The bio-activity of Tagetes erecta on Spodoptera litura.

The bio-activity on the 3rd instar larvaes of Spodoptera litura of different extracts of Tagetes erecta was tested by immursion method in the laboratory,and the highest insecticidal part was screened out.The bio-activity was evaluated after 12 h,24 h and 48 h,with concentration of 625,1 250,2 500,5 000 and 10 000 mg/L,water as CK,using ethanol extracts of marigold flowers,stems,leaves,roots and petroleum ether,chloroform,ethyl acetate extracts and insolubles of marigold roots.The results suggested that all the flowers,stems,leaves,roots and four polar parts of marigold roots had strong contact activity against the 3rd instar larvaes of Spodoptera litura,and in a dose-dependent manner,especially the ethanol extracts and chloroform extracts.The LC50 were 413.56 mg/L and 322.43 mg/L of the ethanol extracts of root after an exposure time of 12 h,48 h,respectively.The activity of chloroform extracts with concentration of 5 000 mg/L and 10 000 mg/L was the strongest,both the corrected mortality rate reached 100% and the LC50