The study of citrus infestation by the black scale Parlatoria ziziphi Lucas 1853 (Homoptera, Diaspididae) is realized between 2012 and 2013 on two citrus varieties (Thomson and Portuguese) in El Fehoul station in Tlemcen in the NorthWest of Algeria. This study shows that Parlatoria ziziphi is present in both varieties and the upper surface of leaves is is always more infested than the lower surfacess. In terms of leaves infestation rates, it's very important at the southern exposure and the center of the plot for Thomson variety and with 100 % in the southern and northern exposure of the Portuguese variety. The rate of fruit fruit infestation is the most important in the south with 87.9 % for Thomson variety and 79 % for the Portuguese variety. The infestation rate of the leaves does not change after harvesting the fruit. This species of scale insect is cosmopolitan and it attacks many species of Citrus family. It is also very common on citrus in Algeria.