The effect of the two entomopathogenic fungi Nomuraea rileyi tested under laboratory green house and field conditions against the potato tuber moth Phthorimaea operculella, results show that the LC50 of the potato tuber moth P. operculella under laboratory conations which cleared that ,it reaches to 76X104 , 98 X104 , 100 X104 and 123 X104, 140 X104 spores/ml for 1st , 2nd, 3rd , 4th , and 5th larval instars., respectively. The corresponding LC50 recorded under semi field conditions, 88X104 , 105 X104, 109 X104, 133 X104 and 149 X104 spores/ ml respectively. When the nano entomopathogenic fungus N. rileyi treat the different larval star of the potato tuber moth under laboratory conditions the result showed that the LC50 of the corresponding stages , 88X104, 105 X104, 109 X104, 133 X104 and 149 X104 spores/ ml for 1st, 2nd,, 3rd, 4th, and 5th larval instar .,respectively. The effect of the nano-entomopathogenic fungi N. rileyi on egg laid/ female were significantly decreased to 11±1.6 eggs/female as compared to 399±6.7 eggs/ female in the control. The percentage of malformed adults reached to 97% after nano N. rileyi. The yield assessment detected that the yield weight obtained 11.995± 50.96and 11.256±91.71 tons/ feddan after treatment with nano N. rileyi and N. rileyi as compared with 8.367±50 in the control during season 2013. During season 2014 the potato weight were significantly increased 12.279±87.66 ton / feddan after nano-N. rileyi treatments.