The seasonal activity of the pine scale, Leucaspis pusilla Löw (Hemiptera: Diaspididae) was conducted for two successive years (Mar., 2009 - mid-Feb., 2011) on Aleppo pine trees (Pinus halepensis) (Pinales: Pinaceae) cultivated at International Center For Training and Development at El-Amriya district, Alexandria Governorate. The obtained results revealed that, L. pusilla has two overlapping generations a year on Aleppo pine trees occurred in spring and autumn seasons. The insect population reached its maximum activity during May and October/November, peaked during May in the 1^st generation and October/ November in the 2^nd one. The shortest generation  occurred in spring with duration of 5.5 months at 21.3 - 22.3ºC and 64.7 - 69.5%R.H. whereas the longest one occurred in autumn with duration of 7 months at 21ºC & 66.4 - 67.6%R.H. The autumn generation is the largest one (495.5 - 557.4 insects) and spring generation is smaller one (336.7 - 360.6 insects). On the other hand, the insect population reached to minimum numbers in summer season. The tested climatic factors (daily mean max. and min. temperatures as well as R.H.%) showed significant effect on the insect population in the both generations in the two years, the changes in the half monthly counts of nymph and adult populations referred to the combined effect of the tested climatic factors on the insect population in the 1^st generation (spring generation) were 56.9 - 57.2% for  nymphal stage; 53.7 - 65.3 for adult stage and 56.4 - 61.0% for insect population (nymph and adult) in the two years, respectively. In the 2^nd generation (autumn generation) were 73.6 - 73.8% for nymphal stage; 62.4 -72.7% for adult stage and 70.7 -73.9%for insect population (nymph and adults) in the two years, respectively.