This investigation was conducted in two subsequent (2014 and 2015) summer seasons, for the purpose of appraising grain yield losses to corn plants (Zea mays L.),  due to attack by the lepidopteran stem borers, Sesamia cretica Led. (Noctuidae), Ostrinia nubilalis (Hb.) (Pyraustidae) and Chilo agamemnon (Bles.) (Crambidae).  Maize plants were treated with the recommended doses of five insecticides:-  Chloropyriphose (Pyreban ® 48%), the novel insecticide Spintoram (Radiant® 12%SC), Indoxacarb (Avaunt® 15% EC), Chlorantranliprole (Coragen® 20% SC) and the natural biological agent Azadirachtin (Achook® 0.15 EC). Obtained data revealed that loss percentages were 0.00, 11.23, 24.60, 28.34, 39.04 and 39.25 for Cholorotraniliprol, Indoxacarb, Spintoram, Chloropyrephose,  Azadirachtin and control, respectively in 2014. In 2015 the corresponding percentages were as follows: Azadirachtin (36.57), Chloropyrephose (30.69) Spintoram (9.97), Indoxacarb (1.10) and 53.62% for the control. As a general observation, the larval number of each species increased maize grain yield loss. Loss percentages are a prerequisite step for the determination of the economic injury level for each borer, according to the procedure indicated by Pedigo and Higley (1996). Econmice injury levels (EILs) due to infestation with  S. cretica were (1.51) for Cholorotraniliprol, (0.93) Indoxacarb, (1.75) Spintoram, (0.83) Chloropyrephose, and (1.31) for Azadirachtin  These levels due to infestation by O. nubilalis  were 2.42, 1.57, 2.68, 1.38 and 1.75; while they were 0.60,  0.39, 0.66, 0.31 and 0.32 due to infestation with  C. Agamemnon when treated with the forementioned insecticides respectively, in 2014. In season 2015 the  corresponding  respective EILs values were 2.08, 1.40, 2.25, 1.26 and 1.87 for Chlorotraniliprol, Indoxacarb, Spintoram, Chloropyrephose and Azadirachtin,  respectively, for S. cretica ; 1.00, 0.69, 1.48, 0.85 and 0.70 for C. agamemnon and  2.33, 1.60, 3.13, 1.57 and 1.75 for O. nubilalis as represented by number of larvae / 10 plant.