Toxicity and feeding deterrence of crude toxin extracts of Lecanicillium (Verticillium) lecanii (Hyphomycetes) against sweet potato whitefly, Bemisia tabaci (Homoptera: Aleyrodidae)

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Abstract
Crude toxins [toxinV3450 and toxinVp28, extracted from Lecanicillium (Verticillium) lecanii (Zimmermann) Gams & Zare strain V3450 and Vp28 respectively] were tested for contact toxicity, feeding deterrence and repellent activity against the sweet potato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Both toxins showed ovicidal activity to eggs, with LC50 values of 447 and 629 mg L−1 respectively. Nymphs of B. tabaci were the most susceptible stages (LC50 values were calculated at 111 mg L−1 for toxinV3450 and 216 mg L−1 for toxinVp28), and adults were the second most susceptible stages (48 h LC50 values were calculated at 178 mg L−1 for toxinV3450 and 438 mg L−1 for toxinVp28). Applied to seedlings at a concentration of 400 mg L−1, the toxins significantly (P < 0.001) reduced the hatching of whitefly eggs and the subsequent survival rate of the nymphs, and the emergence and fecundity of the progeny adults. Both toxins exhibited repellent activity at low concentration (100 mg L−1), with repellency index (RI) values of 0.645 for toxinV3450 and 0.642 for toxinVp28, and antifeedant activity at high concentration (1000 mg L−1) to adults, with antifeedant index (AFI) values of 0.713 for toxinV3450 and 0.749 for toxinVp28. The results of the present study demonstrate the toxicity, repellence and antifeedant properties of the fungi metabolite toxins on B. tabaci, which might develop as environmentally friendly plant protectant(s). Copyright © 2007 Society of Chemical Industry

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