Sunn Pest, Eurygaster integriceps Puton, is the most important pest of wheat and barley in Iran and throughout the Middle East. In this study, different isolates of Beauveria bassiana from overwintering areas in the centre of Iran were collected. In this research, a total of 510 soil samples and cadavers were taken under plants harbouring overwintering Sunn Pest in Semnan, Qum, Kerman and Markazi provinces. The collections were done in late summer and winter 2015 and 2016. The pathogenic fungi were isolated from soil by insect bait method using larvae of wax moth (Galleria mellonella). Data on longitude, latitude, elevation, temperature, soil type and entomopathognic fungi present were recorded for each site. Results indicate that entomopathognic fungi were isolated from 257 of the 510 soil samples, with only Beauveria bassiana and two species Isaria farinosa and Isaria fumosorosea (50.4%). Environmental and geographical impact studies indicated the fungi preferred soil with lower soil temperatures. Significantly more isolates were found at 2300 meters elevation although some were present at 1900 to 2100 meters.