The study was carried out throughout two successive years (2016/2017 and 2017/2018) at Esna district, Luxor Governorate, to recognize the ecological effects of certain climatic factors on the plum scale insect pest, Parlatoria oleae (Colvee) on mango trees to specify the proper timing for control. The obtained results showed that the pest population of P. oleae occurred on mango trees all the years and had three peaks of seasonal activity per year, which was recorded in October, April and July during the first year (2016/2017) and through in November, April and July during the second year (2017/2018). Furthermore, the percentages of infestation incidence by pest showed three peaks per year, during November, April and July in both years. It seems that, the climatic conditions of autumn months during the two years were more suitable for the total population density and its activity and the maximum values of the infestation incidence by P. oleae. The obtained results showed that, the effect of weather factors (mean daily of air temperature, mean of relative humidity and mean of dew point) on the pest population and on the percentages of infestation incidence during the two successive years emphasized that the effect of these factors varied from year to another. Also, the dew point was the most effective variable for the changes in the pest population and the percentages of infestation incidence by the pest during both years and on the two cumulative years.