Ecological studies on San José scale, Diaspidiotus perniciosus (Comstock) (Homoptera: Diaspididae) as a new insect pest on pear trees in Burg El-Arab area, Alexandria, Egypt.

The San José scale, D. perniciosus (Comstock) (Homoptera: Diaspididae) was noticed on pear trees all the year round in Burg El-Arab area (50 km West of Alexandria). Bio ecology and population fluctuations of this serious scale insect were carried out during the two subsequent seasons of September, 2004 until August, 2006. The calculated infestation rates (%) assured the presence of three peaks in both seasons. The estimated densities of fluctuating individuals of D. perniciosus on the inspected pear trees showed two distinctly prominent peaks, in addition to an overlapping one between them. It means, that the San Josè scale, D. perniciosus had three overlapping annual generations on pear trees in Burg El-Arab area under an irrigation system. The individuals of all stages could be found on trees all over the year. The population of the inspected immature stages; adult females and adult males were recorded and discussed as well as the parasitized individuals by the aphilinid parasitoid, Aphytis diaspidis (Howard) (Hymenoptera: Aphelinidae). The population density of the San José scale (SJS) reached its maximum during spring, folLowed by summer, winter, whereas the least percentage was recorded in autumn months. The obtained data showed also variable effects of the prevailing abiotic factors on the dynamical oscillation of (SJS) individuals. The daily mean temperature and the dew point were not the dominant efficient physical factors. On the contrary, it has been proved that there were either significant strong negative or positive relationships between daily relative humidity, wind speed, infestation rate, and population density of this studied insect pest.