The present study were carried out during seasons 2009/10 and 2010/11 in Qalubia Governorate. The citrus mealybug Planococcus citri (Risso) nymphs had four peaks of abundance during the first season in 14^th June 2009, 9^th August 2009, 13rd December 2009 and 21^st February 2010. Moreover, the insect adults had also four peaks of abundance in 17^th May 2009, 28^th June 2009, 9^th August 2009 and 21^st February 2010. While in the second season insect nymphs had five peaks of abundance in 18^th April 2010, 25^th July 2010, 3^rd October 2010, 28^th November 2010 and 20^th March 2011. While the insect adults had also five peaks of abundance in 2^nd May 2010, 3^rd October 2010, 14^th November 2010, 26^th December 2010 and 3^rd April 2011. Six citrus species were screened during two seasons for susceptibility to citrus mealybug P. citri in Qalubia orchard. In the first season 2009/10 Clemantine mandarine and Balady mandarine were the least infested species by the insect with the mean numbers of 20.9±3 & 21.4±2.1 nymphs and 12.8±1.9 & 9±0.8 adults, respectively. While, Sour orange and Lemon were the heaviest attacked by the insect with the mean numbers of 152.3±17.5 & 150.3±8.8 nymphs and 84.3±10 & 76±4.7 adults, respectively. Navel orange and Persian agami were moderately infested by P. citri with the mean numbers of 58.1±6.7 & 38.7±5.8 nymphs and 33±4 & 23.7±3.8 adults, respectively. In the second season Lemon and Sour orange were the heaviest infested by the insect with the mean numbers of 172.2±21.1 & 119±8.3 nymphs and 104.1±13.8 & 67.7±5.4  adults, respectively. While, Persian agami and Navel orange were moderately susceptible to infestation where the recorded mean numbers were 32.8±2.1 & 52.5±6 nymphs and 18.5±1.6 & 27.9±2.5 adults, respectively. Clemantine mandarine and Balady mandarine were the lowest susceptible to infestation with the mean numbers of 23.2±4.9 & 32.3±6 nymphs and 11.4±2.2 & 18.4±3.4 adults, respectively. 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 oil had longer residual effect and less harmful to natural enemies.