Six citrus species were screened during 2009/2010 for susceptibility to citrus mealybug Planococcus citri in Qalubia orchard. Clemantine mandarine and Balady mandarine were the least infested species by the insect, while Sour orange and Lemon were the heaviest attacked by the insect. Navel orange and Persian agami were moderately infested by P. citri. Volatile oils were analyzed in tested citrus species so that different levels of susceptibility in citrus species to P. citri infestation may be correlated to different kinds and percentage of components of volatile oils. Sour orange which was the heaviest infested was characterized by the highest rates of Champhor and Linalool, and Lemon which came the next after Sour orange showed highest rate of Carvon and d-limonene. The efficacies of four insecticides (Confidor 20% SL., Vertimec 1.8% EC, Castor oil 30% and Mesrona oil 85% EC) against P. citri on 35 – years – old trees of Navel orange were evaluated. Mortalities were recorded after 3, 7, 14, 21 and 30 days of treatment. Confidor was the most effective compound followed by Vertimec, while Mesrona oil and Castor oil gave reductions in population rate after 30 days from application to 82.2 and 68.6% respectively. Three weeks later, the activity of both Confidor and Vertimec had decreased rapidly, however mineral oilhad longer residual effect and less harmful to natural enemies