Comparative analysis of three scale insect species populations (Hemiptera: Coccoidea: Diaspididae) and their parasitoid, Aphytis diaspidis(Howard) on pear trees in Burg el-Arab area, Alexandria, Egypt.

The infestation abundance of each of the inspected scale insect species: San Jose scale, Diaspidiotus perniciosus (Comstock), Greedy scale, Hemiberlisio rapax (Comstock) and Olive scale, Parlatoria oleae (Cloveé) on pear trees, more or less varied as the months of each growing season differed. The comparative abundance percentages in both seasons of 2004-2005 and 2005-2006 were (51.80 and 51.40), (41.20 and 40.90) and (7.10 and 7.70) of the counted individuals of the grand total of H. rapax, D. perniciosus and P. oleae, in respect. In other words, the Greedy scale (GS) was the highly abundant scale followed by the San Jose scale (SJS), but the olive scale represented the lowest one. The more or less increased and/or decreased abundance of each of the investigated scale insect species pointed to the existence of three overlapping generations throughout the season which were characterized by fluctuating peaks of population densities of the studied pests during the months of each annual season: autumn, winter, spring and summer.