The present investigation was carried out at Esna district, Luxor governorate during 15 September 2011, to determine the role of the two main essential nutrients and their inhibitors in susceptibility of five date palm varieties to infestation by Parlatoria blanchardi (Targ.). Date palm varieties varied significantly in their susceptibility to P. blanchardi. White variety was the highest infestation with the pest (23.9 insect/leaflet) and exhibited the highest concentrations of crude proteins, total carbohydrates and food quality index, but had exposed the lowest concentrations of both total tannins and phenolsin the infested leaflets compared with other the tested varieties. In contrast, Gendeila variety was the least infested variety by this insect (8.2 insect/leaflet). While, Malakaby, Seedy Balady and Shamia varieties were moderately infested with mean number of 17.2, 15.7 and 12.9 insect per leaflet, respectively. The levels of total soluble carbohydrates and crude proteins of infested date palm leaflets for all tested varieties were lower than those of the uninfested ones, while, tannins and phenols were lower in the uninfested varieties than in the infested ones. In addition, the increase in concentrations of soluble condensed tannins and phenols in leaflet might be due to an decrease in population density of insect in Shamia variety. Also, may be  play a role in the defense mechanism of P. blanchardi infested date palm leaflets, thereby delay their death. It is clear that the highest percentage of reduction in crude proteins, carbohydrates and food quality index was measured in infested leaflets of White date palm variety as compared with the uninfested ones. The results revealed highly significant positive correlations between the rate of infestation by P. blanchardiand the percentage of reduction in crude proteins, carbohydrates and food quality index. In contrast,there wereinsignificant negative correlations between insect infestation and the percentage of reduction in tannins, fats and phenols. The loss in the measured parameters was a summation of many factors including level of infestation, time of infestation, variety and essential nutrients and inhibitors of leaflets. The relative role of these factors may differ among different varieties.