Insecticidal activity of different fractions of distilled oil extracted from Eupatorium adenophorum against 4 species of stored grain insects.

The fractions of essential oils extracted from Eupatorium adenophorum Spreng at different temperature were used in fumigation at the rate of 44.44 mg/L to control the adults of rice weevil [Sitophilus oryzae (L.)], maize weevil (S.zeamais Motschulsky), adzuki bean weevil [Callosibruchus chinensis (L.)] and European bean weevill (Bruchus rumimanus Boheman). The fraction extracted at 150℃～200℃ showed the highest inseticidal activity against all the 4 species of insects, followed by the fractions extracted at 20℃～150℃ and 200℃～230℃. The fraction extracted at 300℃ or higher temperature had the lowest insecticdal activity. Bioassay indicated that the LC 50 of the fraction 150℃～200℃ of 24-h fumigation to the adults of rice weevil, maize weevil, adzuki bean weevil and European bean weevil was 15.5114, 17.8124, 18.0302 and 16.2671 mg/L, repsectively.