Insecticidal activity of Melia toosendan extracts and toosendanin against three stored-product insects
1995
Xie, Y.S. | Fields, P.G. | Isman, M.B. | Chen, W.K. | Zhang, X.
Repellency, toxicity, and fecundity-reducing effects of bark extracts of Melia toosendan on three stored-product beetles, the rusty grain beetle, Cryptolestes ferrugineus (Stephens), the rice weevil, Sitophilus oryzae (L.), and the red flour beetle, Tribolium castaneum (Herbst), were investigated in the laboratory. Wheat kernels treated with extracts containing 75 and 3% toosendanin at concentrations from 0.05 to 0.4% (375-3000 ppm toosendanin), and from 0.5 to 2.5% (150-750 ppm toosendanin), respectively, repelled beetles by 50-98%, compared with controls. The test materials were more toxic to S. oryzae than C. ferrugineus and were not toxic to T. castaneum. The LC(50) values for the extract containing 75% toosendanin for S. oryzae and C. ferrugineus after 6 weeks exposure were 675 and 1875 ppm toosendanin, respectively. Both extracts significantly reduced F(1) adults of all three insect species in most treatments. Pure (98%) toosendanin caused only 4% mortality of C. ferrugineus and S. oryzae at a concentration of 0.15% (1470 ppm toosendanin) after 2 weeks, but significantly reduced the F(1) adults compared with controls. This study indicates that a natural grain protectant based on M. toosendan extracts may be feasible.
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