The work consists of a study on the level of infestation of the 3 species of olive-infused mealybugs at the two stations (Soumaa and Guerrouaou) in the Blida région, with particular attention to the évolution of Pollinia pollini (Asterolecanidae), Octaspidiotus nerii (Diaspididae) and Saissetia oleae (Lecanidae). Unlike the Soumaa station, there is a large infestation in the Guerrouaou station by the three (most abundant) species with a high rate. The life cycle monitoring and the bio-ecology of these three pests were carried out through periodic population counts on the leaves and twigs of the tree from 08 August 2016 to 29 May 2017 in the wilaya of Blida. It appears that the study of the biology of P.pollini evolves in 2 annual generations (the first is the spring generation; the second is through the summer. The larval stage remains the most abandoned compared to other developmental stages. The South orientation seems the most affectionate by P.pollini. We can conclude that O .nerii has two generations « spring and automne » depending on climatic factors. The East and West exposure represent the places most sought after by this scale where we found a relative abundance between larvae and adult females. S. oleae develops only one generation per year (automnal génération). Females are the most abundant in Soumaa station and larvae in Guerrouaou station. The eastern orientation and the automne season are the most favourable for the development of the mealybug.