الفهرس 
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Abstract
Objective : 1. Investigation of host plant – Quadraspidiotus perniciosus interactions 2. Monitoring the seasonal population trends of SJS and their associated predators in apple orchard. 3. The response of Q. perniciosus population to the changes in temperature and relative humidity. 4. Influence of host plant species on the population dynamics of Q. perniciosus. 5. Life and fertility tables of Q. perniciosus on different host plant species. 6. Determination the searching rate and mutual interference of some coccinellid predators as bio-control agents against Q. perniciosus. Methods & Results 1. The highest score of infestation by San Jose scale (SJS), Q. perniciosus was found on apple trees, with an average of 1.10±0.79. The sex ratio of Q. perniciosus was low on plum and pear trees in comparison with that on apple trees. 2. During the course of the present study five insect predators were recorded with relatively high number on apple trees .In addition to four hymenopterous parasitoids were recorded on SJS population .Statistical analysis indicated that there was positively high significant correlations between both percentage of predatism and unknown mortality with total population mortality during the first (r = 0.71 and 0.67) and second (0.76 and 0.79) years. 3. Life table data showed considerable changes in the numbers of Q. perniciosus entering each stage from one generation to another with respect to stage- specific mortalities, natural mortality destroyed a higher proportion of the 2nd instar female nymph than of the white cap and the adult female stages. There was a considerable variation among host plant and generations in the contribution of each stage specific mortality to the total generation mortality (K). However, changes of k2 values were more correlated with the changes of k-value of the total generation mortality in all tested host plants. 4. The host plant had an effective role on the population dynamics of the diaspidid, San Jose Scale Q. perniciosus. 5. For the success of IPM program it is essential to know several biological aspects of the pest on the targets host and their natural enemies. 6. The coccinellid predators promise to be good biological control agent against the tested diaspidid species, especially, Chilocorus bipustulatus. However, it exhibited higher searching rate with low matual interence value.