ABSTRACT Four native isolates of the entomopathogenic fungus Nomuraea rileyi were isolated from soil samples collected from 210 different irrigated and non-irrigated tomato-growing fields in the West Bank-Palestine. The four isolates were recovered from soil samples collected from the Jenin area during August 2006 (Nr 3, Nr 5, Nr 17 and Nr 18), and were then deposited at the US Agriculture Research Service collection of Entomopathogenic Fungi (ARSEF 7794, ARSEF7793, ARSEF7792 and ARSEF 7791). The isolation was carried out by using dilute plate technique on modified selective medium. The medium used in the study was based on the standard Saboraud's maltose agar yeast extract, and modified by adding Tween ® 80 and the fungicide dodine . The results showed that the LT 50 for these isolates at the inoculum concentration of 10 8 spore ml -1 were in the range of 7.9 to 9.4 days. The LC 50 was in the range of 10 5 and 10 6 spore ml -1 . The virulence of the most promising isolate (ARSEF 7794) compared to the insecticide Thyonex ® was evaluated on H. armigera under tomato open field conditions; the results showed that the fungus and the insecticide reduced tomato infestation by 46%, and 88% respectively, compared to the control
