Susceptibility of the immature and adult stages of the sweetpotato whitefly (Homoptera: Aleyrodidae) to selected insecticides
1989
Prabhaker, N. | Toscano, N.C. | Coudriet, D.L.
We determined the toxicity of malathion, methyl parathion, monocrotophos, sulprofos, permethrin, and neem seed extract to various life stages of susceptible and resistant populations of sweetpotato whitefly, Bemisia tabaci (Gennadius), in the greenhouse. All insecticides were most active against first-stage larvae, with the lowest LC50's ranging from 0.001 to 0.014 mg/ml for the synthetic insecticides and 1.44 mg/ml for neem seed extract. Toxicities decreased between successive stages. LC50's were always higher for the egg and pupal stages. Adults of the resistant strain were the most tolerant regardless of the insecticide tested, with LC50's ranging from 2.824 to 25.50 mg/ml. First-stage larvae were the least resistant to all the insecticides (resistance ratio [RR] = is greater than 2-fold), with resistance increasing to moderate levels in pupae (RR = 5.5-12.3-fold) and to high levels (RR = 46.3-108.6-fold) in adults. Neem seed extract was the least toxic material to any of the stages; however, no resistance to neem was detected in any stage.
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