干旱区生态环境知识资源中心

Based on random samples of leaves taken at about fortnightly intervals from four Ficus nitida trees, studies on the population dynamics of the oriental scale, Aonidiella orientalis (Newstead) and factors affecting its seasonal abundance were carried out throughout the year 1987-1988. Counts of alive scales were made on 1 sq. inch per each leaf surface.

Four distinct peaks representing four annual generations were observed; two winter and two spring generations. During summer, the population attained its lowest level probably due to the extremely high temperature and arid climate prevaling during this period of the year. A steady increase in the population of insects was observed in autumn, and the first peak of abundance appeared at the beginning of winter.

Temperature was negatively and significantly correlated with the population, values of (r) for the maximum and mean temperatures obtained (-0.6667 and -0.5995 respectively) were highly significant. On the other hand, rainfall had no apparent effect on the population (r = 0.2813), while correlation with the relative humidity was slightly positive (r = 0.4897). As a general rule, the sides of trees exposed to the winds harboured less individuals than the opposite sides. Crawlers seem to be forced to drift by wind to more protected zones.