| The glasshouse whitefly, Trialeurodes vaporariorwn (Westwood) and the green peach aphid, Myzus persicae (Sulzer) are major pests of vegetables throughout the world. Control of whiteflies by chemicals pollutes the environment, so alternatives are urgently needed such as biocontrol using entomopathogens.Verticillium lecanii is a worldwide hyphomycete fungus that has been developed as a biocontrol agent against whiteflies and aphids. Since the early 1970s, it has been known primarily as a pathogen of homoptera insects, mainly aphids and scales, although it has also been isolated from spiders and mites. V. lecanii is also a mycoparasite of rust, powdery mildew, green mold, and nematodes. In Europe, two strains of V. lecanii have been commercialized for the control of aphids and whiteflies. Therefore, the pathogen has great potential for biological control of insect pests and plant diseases.Isolation of strains of V. lecanii for different pest whiteflies or aphids plays an important role in improving the pathogenicity of this fungus. Furthermore, the Vp strain is also been applied in greenhouses for testing the control effective of glasshouse whitefly.First of all, the pathogenicity of Vp to the green peach aphid, M. persicae is evaluated in the laboratory and the median lethal concentration required to achieve 50% mortality (LC50) were obtained at different treatments. The results showed that this pathogen is active against the green peach aphid. The LC50 at 23℃ was 2.48× 105 conidia/ml, while at 30℃, the LC50 was 4.16× 106 conidia/ml. V. lecanii showed almost no virulence to aphid at 12℃. Furthermore, we comparied the pathogenicity of V. lecanii with Beauveria bassiana, and the result showed that V. lecanii is more virulent than B. bassiana.We then tested the Vp strains against whiteflies in greenhouses. We investigated the infection rate of whiteflies two weeks after spraying with V. lecanii. The pathogen reduced the adults, nymphs and eggs of whitefly by 72.45%, 25.09% and 73.69%, indicating good adult control, while no virulence to Encarsiaformosa.To find ways of getting even better control, we isolated new strains of V. lecanii. Twenty strains were obtained and many of them induced high mortality of the whitefly and the green peach aphid. The various strains caused whitefly mortality ranging from 48.79-86.69%, with LC50 values varying from 6.01× 104 to 1 .93× 107 conidia/ml. The most active strain of V. lecanii to the whitefly is V4, which had an LC50 of 6.01× 104 conidia/ml, and the higher strain is V8 with LC50 of 6.43 × 104 which both of them show the better quality of pathogenicity to whitefly than Vp, while poorest is V11 with an LC50 of 1.93× 107 conidia/ml.The strains caused aphid mortality of 34.16-82.37%, with LC50 values varying from 2.45× 104 to 7.89× 1010 conidia/ml. The most active strain of V. lecanii to the green peach aphid is V15, which had LC50 of 2.45× 104conidia/ml, but strains V17, V17, and V19, with LC50 values were only slightly higher, 3.56× 1 04 conidia/ml, 4.77× 104conidia/ml, 4.66× 105conidia/ml, all of the four strains are better than Vp in pathogenicity to aphid. The poorest strain was V6, with an LC50 of 7.70 × 1010 conidia/ml. Further work is now required in applying these new strains to pest in greenhouses.
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