Laboratory experiments were carried out to study the degree of insect infestation by Sitophilus oryzae L. on maize grains (Hybrid 10) treated in the field with organo-fertilizer (farm- yard manure at zero and 20 m3/Fed.) under three levels of nitrogen fertilization (45, 90 and 135 kg/Fed.). Results showed that the degree of infestation and the mean of emerged adults of 5.  oryzae were greatly affected by the tested fertilization treatments of Hybrid 10 maize. Data also, showed that the treatment with nitrogen fertilizer alone gave a susceptible hybrid to insect infestation whereas, the combination between the high levels of nitrogen (135 kg/Fed.) and 20m3/Fed manure, gave Hybrid 10 more tolerant for infestation and with less weight loss. Relationship between some chemical and physical characters of Hybrid 10 and its resistance to insect infestation was also studied. Such characteristics were obviously affected as a result of tested levels of Nitrogen fertilization as well as its combination with manure. On the other hand, some physical characteristics were variously affected by insect infestation, i.e. weight of 100 grain, grain volume, ash % endosperm %, germ % and hull %. Most of chemical composition of tested treatment (except total carbohydrate) were increased by increasing the fertilization i.e. amylose %, protein %, ash, oil %, and fibers. Finally, crude fiber and its fractions in the tested hybrid affected the degree of insect infestation and should be taken in consideration during breeding programs to select a line with high yield, high quality, more resistant to insect attack and characterized with low degree of deterioration after storage.