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Abstract The work presented in this thesis was, conducted on the plum scale insect, Parlatoria oleae (Colvee), infesting pear, plum and apple trees, at El- Quanater El-Khairiya, Menia El-Kamh and Nobariya locations, representing three Egyptian governorates, from Januaiy 1993 to December 1995, to study the population abundance of P. okae on the three studied host plants, the effect of tree heights and cardinal directions on its distribution, the effect of some meteorological factors on the insect abundance, susceptibility of pear, plum and apple trees to infestation with the concerned insect, also susceptibility of the plum varieties to infestation, survey of natural enemies associated with the insect infestation at the three studied locations, studies on the main parasitoid of P. oleae, Aphytis maculkornis and factors affecting the rate of parasitism, the effect of some tested insecticides on the plum scale insect, and finally, the effect of the same tested insecticides on the parasitoid, consequently, on the rate of parasitism. The obtained results may be summarized as follows: 1- Population Abundance of P. oleae: A- On pear trees, at El-Quanater El-Khairiya location: a- Seasonal fluctuations in total population: Two peaks of seasonal abundance were determined, in May (highest peak of an average of 10181 individuals/30 branches) and September (8162/30 branches). The lowest abundance occurred during January, February and August (3004, 2821 amd 3780 individuals/30 branches, respectively). The monthly rates of change in the total population were also recorded and indicated highest increasing rates in March (an average of 1.94) and September (2.17), while the severest decreasing rate was recorded in June (0.62). b- The adult, non-ovipositing females fluctuations: The non-ovipositing adult females showed two peaks of abundance, in June (an average of 3249 individuals/30 branches), and in November (higher peak of 4725), accompanied also with high rates of population increase (2.8 and 1.22 in June and November, respectively). The severest rate of decrease in population was recorded during May (average rate of 0.61). c- The ovipositing females fluctuations : Two peaks of population abundance were also recorded, in April (an average of2056 individuals/30 branches), and September (1660/30 branches), while these insect individuals completely disappeared during January and December, and of very low abundance during February and November. The highest increasing rates were detected in March (16) and August (2.84), whereas the sharpest rate of population decrease occurred in October, being of an average of 0.3. d- The nymphal stage fluctuations: This stage also showed two peaks of abundance annually, in May (7522/30 branches), and September (4094/30 branches), whereas this stage was completely absent during December and January, and in few numbers during February. population was found to be badly affected by the high temperature of August, also by low temperature of January, February and December. The highest rates of nymphs increase occurred in April (average of 4.04) and September (3.89), whereas the lowest rates were detected in June (0.31) and November (0.24). e- Number of generations on pear trees, at El-Quanater EI-Khairiya location: Depending n the relative abundance of nymphs in relation to the total population of P. oleae, the insect mostly, has three integral generations per year; the first starts in March and reaches its peak of abundance in May, subsequently ends in June. The second starts in June, reaches its peak during July and ends in August, while the third starts during late August and continuous to the next February or March, as adults hibernate during winter as gravid females. f- Age-structure of p. oleae on pear trees: The non-ovipositing females were the most abundant individuals throughout the year (constituting average of 47.14- 48.03 % of the total population), followed by the nymphs (36.94-37.77 %) and the ovipositing females, which comprised about 15.13 % of the total population. B- On phi in trees, at El-Quanater El-Khairiya location: a- Seasonal fluctuations in total population: Two main peaks of total population abundance were recorded, in May (often average of 3974 individuals/30 branches) and September (highest peak of 4258/30 branches), indicating an opposite situation to that occurred on pear trees. The lowest insect total population occurred in February, being as an average of 1327 individuals/30 branches, respectively. The highest rates of increase occurred during March (2.20) and September (2.24), while the severest rate of population decrease was in December (0.63). The adult, non-ovipositing females fluctuations : Two peaks of annual activity were detected, in June (where an average of 1343 individuals/30 branches), and in November (highest peak of an average of2919/30 branches). The lowest populations of these individuals were detected during April (534/30 branches), May (500/30 branches) and August (637/30 branches), as an average of the three studied years. The highest increasing rates were recorded in June (2.77) and September (1.93); while the severest rates of decrease were observed during April (0.60) and July (0.61). |