The black parlatoria scale insect, Parlatoria ziziphi (Lucas) is one of the most important armored scale insect infesting citrus trees. This investigation was conducted at Inshas El-Raml district, Sharkia Governorate throughout the two seasons 2016-2017 and 2017-2018 to study some ecological aspects of this scale insect on navel orange trees. This study showed that the seasonal activity of this insect was more abundant in the first season than in the second one, due to the relation with its associated parasitoid. The P. ziziphi had three generations and two peaks of the total alive stages during winter and autumn seasons throughout the two years of investigation. Also, the increase or decline of populations was correlated with some climate factors as temperature, relative humidity and light intensity and also influenced by some chemical components in navel orange trees. These results can be beneficial when developing an integrated program for control this pest without the use of pesticides that may pollute the environment.