Al-Ahmed, A.M.N. 1989 . Survey of scale insects of certain fruit and shade trees in Riyadh Region, with special refrence to the study of the population dynamics and natural e M.Sc. Thesis, Department of Plant Protection, College of Agriculture, King Saud University Ruadh, Saudi Arabia

Notes: A general survey of scale insects infesting fruit trees, shade trees and ornamental plants in Riyadh region, their host plants and natural enemies was carried out throughout the year 1987-1988. Based on random samples of 160 leaves taken at about fortnightly intervals from 4 Ficus nitida trees in the orchard of the Agricultural Experimental Station at Deirab, studies on the population dynamics of the oriental scale insect, Aonidiella orientalis (Newstead) throughout the year were made. The factors affecting its population and mode of its distribution on infested trees were also studied. Counts of alive and parasitized scales were made on 1 sq.inch per leaf surface. Results could be summarized in the following: Ten species of scales belonging to 4 families were encountered in Riyadh region; Aonidiella orientalis, Parlatoria blanchardi (Targ.), Parlatoria crypta McKenzie and Contigaspis Zillae (Hall) (Diaspidiae); Lecanodiaspis africana Newstead (Lecanodiaspididae); Asterolecanium phoenicis Rao (Asterolecaniidae); Parasaissetia nigra (Nietner) , Coccus hesperidum Linn. , C. longulus (Douglas) anc Saisseria oleae (Coccidae) .