Abstract: The objectives of this study were to evaluate the efficacy of Sunn pest entomopathogenic fungi collected from wheat fields and overwintering sites in Syria and characterize them under different temperature regimes. Eleven isolates of Beauveria bassiana (Bals.) Vuil. were included in this study: five were isolated from overwintered adults of Sunn Pest, Eurygaster integriceps Puton and six from nymphs and new adults in wheat fields. Growth rate and conidial production were tested at 15, 20, 25, 30 and 35°C. Results showed that highest growth rate of tested fungal isolates was at 25°C, except for the two isolates SPDR-1 and SPDR-2 which exhibited highest growth rate at 20°C. The highest production of conidia of tested fungal isolates was at 20°C, except for isolates SPSR-1, SPSQ and SPSS which exhibited higher production at 25°C. Virulence test of the tested fungal isolates on overwintered adults Sunn Pest showed that percent mortality after 14 days ranged between 86-100%.