Abstract: A fungus strain CHLB5 isolated from soils from Cuba has been identified as Lecanicillium attenuatum based on the morphological characteristics and molecular analysis of ITS-rDNA. This fungus was able to use many kinds of carbohydrates and nitrogen for mycelia growth and sporulation. Maltose and peptone were the best carbon and nitrogen for mycelia growth with growth rates of 6.38 and 7.44 mm/d respectively; glycerol and ammonium sulfate were the worst for mycelia growth with growth rates of 3.92 and 3.79 mm/d respectively. The sources of carbon and nitrogen were very important for the conidial production of this strain. Maltose and peptone were the best carbon and nitrogen for conidial production with 6.98×10¹⁰ and 3.96×10¹⁰ conidia per dish on PDA for 7 d respectively; glycerol and urea were the worst for conidial production with 0.39×10¹ and 1.76×10¹⁰ conidia per dish respectively. This fungus was able to grow and produce spores at 19—29 ℃ with the optimum at 27 ℃. The pathogenicity tests showed that the treatment with this fungus resulted in 86.9% mortality in the second instar nymphs of Bemisia tabaci at 8 days. These results indicated that this fungus strain CHLB5 might be a potential agent for biological control against B. tabaci..