Various fungicides and pesticides often have been used in agricultural environment for controlling diseases and pests. These pesticides can have detrimental effects on entomopathogenic fungi which have pest controlling ability. In this study of 10 fungicides was investigated on mycelial growth and conidia germination rate of Botrytis cinerea , Lecanicillium muscarium and Beauveria bassiana . By evaluating of conidia germination of fungicide-treated fungi, Benomyl with IC50 equal to 0.218 and 0.048 mg L -1 had the highest inhibitory effect on B. bassiana and L. muscarium respectively and Carbendazim with IC50 equal to 0.097 mg L -1 and after that Benomyl, Mancozeb, Stroby, Chlorothalonil, Iprodione+Carbendazim, Captan and Zineb had the highest inhibitory effect on B. cinerea . Copper oxychloride with IC50 equal to 1380.94 mg L -1 had the lowest inhibitory effect on B. bassiana and Bordeaux mixture with IC50 equal to 147.6 and 1096.902 mg L -1 had the lowest inhibitory effect on L. muscarium and B. cinerea respectively. Mycelial growth of fungicide-treated fungi were investigated after 3 and 7 days and in both time periods, Carbendazim with IC50 equal to 0.015 and 0.016 mg L -1 had the highest inhibitory effect on L. muscarium after 3 and 7 days respectively and also it had the highest inhibitory effect on B. bassiana with IC50 equal to 0.076 mg L -1 after 3 days and 0.112 mg L -1 after 7 days. Benomyl with IC50 equal to 0.036 mg L -1 had the highest effect on mycelial growth on B. cinerea after 3 and 7 days and also the fungicides Carbendazim, Iprodione+Carbendazim, Stroby, Chlorothalonil, Mancozeb, Zineb, Bordeaux, Captan and Copper oxychloride had respectively the most effect on mycelial growth of this fungus after 3 days. In this study the effect of fungicides Copper oxychloride, Benomyl and Iprodione+Carbendazim which are currently-used fungicides on controlling B. cinerea was investigated on pathogenic fungi in controlling whitefly Bemisia tabaci with field recommended, half field recommended and duplicated field recommended concentrations. In this study Benomyl and Iprodione+Carbendazim with duplicated field recommended concentration had the highest and Copper oxychloride with half field recommended concentration had the lowest effect on competency of these fungi. In investigating of the effect of fungicides on preventing rate of wound expension affected by B. cinerea it is determined that Benomyl treatment with wound diameter by 0.73 mm and Copper oxychloride treatment with wound diameter by 6.16 mm had the highest and the lowest effect on prevention of expansion of this fungus on the fruit respectively. Different strains of B. cinerea were collected from various areas in Isfahan and the effect of fungicides on their conidial germination was also studied. The results showed that these strains have differences regarding sensitivity and resistance to 10 studied-fungicides. Obtained results showed that the fungicides from Benzimidazoles are of the most effective fungicides on mycelial growth rate and conidial germination of fungi B. cinerea, L. muscarium and B. bassiana and cupreous fungicides such as Copper oxychloride and Bordeaux mixture have the lowest effect on mycelia germination and growth on these fungi. It is also showed that the competency of Entomopathogenic fungi on controlling whitefly has decreased by using these fungicides. Key words : Botrytis cinerea Entomopathogenic fungi, fungicides, strain, whitefly