الفهرس 
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Abstract
The present study was conducted throughout two successive years (from January 1^st, 2021 until December 15^th, 2022) on date palm trees, Phoenix dactylifera L. (Family: Arecacea) in two districts New-Damietta and Faraskour, Damietta governorate, Egypt. The selected date palm trees received the normal agricultural practices, without pruning the fronds or applying any chemical control measures, before and during the period of investigation. Five palm trees were selected from each district to carry out these studies. selected palm trees for study were similar in size, shape, height and vegetation.
The obtained results could be summarized as the following points:
5.1. The population fluctuation of the white date palm scale insect, Parlatoria blanchardi:
5.1.1. In New Damietta district:
The population fluctuation of the total and alive individuals of the white date palm scale insect, P. blanchardi was observed during the two successive years (2021 and 2022) in New Damietta district. The insect had six peaks of abundance during the first year and seven peaks during the second year for each total and alive individuals. The highest peaks occurred in beginning of January, 2021 and Mid-November, 2022 for the total individuals and both represented by 1520 and 1362 scales / 100 leaflets, respectively. In respect to alive individuals, the highest peaks occurred in beginning of December, 2021 and Mid-November, 2022 and both represented by 778 and 968 alive individuals / 100 leaflets, respectively. The annually average number of the total individuals recorded the highest during the second yea,r 2022 than the first year, 2021 and represented by 686.1 ± 294.53 and 617.6 ± 396.38 scales / 100 leaflets, respectively. Moreover, the annually average number of the alive individuals recorded the highest during the second year than the first year and represented by 453.2± 222.29 and 342.7± 205.30 alive individuals /100 leaflets, respectively.
5.1.2. In Farskour district:
The population fluctuation of the total and alive individuals of the white date palm scale insect P. blanchardi was observed during the two successive years (2021 and 2022) in Farskour district. The insect had six peaks of abundance during the first year and seven peaks during the second year for each total and alive individuals. The highest peaks occurred in beginning of February, 2021 and Mid-October, 2022 for the total individuals and both represented by 1156 and 1552 scales / 100 leaflets, respectively. In respect to alive individuals, the highest peaks occurred in Mid-September, 2021 and Mid-October, 2022 and both represented by 784 and 1102 alive individuals /100 leaflets, respectively. The annually average number of the total individuals recorded the highest during the first year, 2021 than the second year, 2022 and both represented by 605.7 ± 303.38 and 546.2 ± 421.26 scales / 100 leaflets, respectively. Moreover, the annually average number of the alive individuals recorded the highest during the second year than the first year and both represented by 355.8 ± 304.26 and 352.0 ± 169.58 alive individuals /100 leaflets, respectively.
5. 2. The seasonal effects of the different mortality factors:
5. 2. 1. Predation
5. 2. 1. 1. In New Damietta district:
The seasonal abundance of the predators as number of preyed individuals on the white date palm scale insect, P. blanchardi was recorded during the two successive years (2021 and 2022) in New Damietta district. The highest number of preyed individuals were recorded in beginning of January during the first year and beginning of February during the second year and both represented by 18 and 28 individuals, respectively. January, 2021 had the highest preyed individuals and percentage (17 indiv. and 16.67%), while, February, 2022 had the highest preyed individuals and percentage (25 indiv. and 15.82%). The annual average number of preyed individuals were the highest during the second year than in the first year and both represented by 13.2 ± 5.89 and 8.5 ± 3.45 individuals, respectively. 5. 2. 1. 2. In Farskour district:The seasonal abundance of the predators as number of preyed individuals on the white date palm scale insect, P. blanchardi during the two successive years (2021 and 2022) in Farskour district. The highest number of preyed individuals were recorded in beginning of January and beginning of September during the first year and Mid-January during the second year and both represented by 20 and 24 individuals, respectively. January, 2021 had the highest preyed individuals and percentage (18 indiv. and 15.13%) as well, January, 2022 had the highest preyed and percentage (22 indiv. and 12.09%). The annual average number of preyed individuals was the highest during the second year than the first year and both represented by 15.2 ± 3.51 and 9.9 ± 4.46 individuals, respectively.5. 2. 2. Parasitism by the ectoparasitoid, Aphytis spp.5. 2. 2. 1. In New Damietta district:The seasonal abundance of the immature stages of the ectoparasitoid Aphytis spp. had the highest number in January for the two successive years (2021 and 2022) in New Damietta district. The annually average number of the immature stages of Aphytis spp. was the highest during the first year, 2021 than the second year, 2022 and both represented by 16.6 ± 15.12 and 11.5 ± 6.78 individuals, respectively.5. 2. 2. 2. In Farskour district:The seasonal abundance of the immature stages of the ectoparasitoid Aphytis spp. had the highest number in January for the two successive years (2021 and 2022) in Farskour district. The annually average number of the immature stages of Aphytis spp. was the highest during the first year, 2021 than the second year, 2022 and both represented by 13.6 ± 14.39 and 5.2 ± 3.19 individuals, respectively. 5. 2. 3. Parasitism by the endoparasitoid, Encarsia citrina 5. 2. 3. 1. In New Damietta district:The seasonal abundance of the immature stages of the endoparasitoid E. citrina had the highest number in January for the first year, 2021 and Mid-March for the second year, 2022 in New Damietta district. The annually average number of the immature stages of E. citrina was the highest during the first year, 2021 than the second year, 2022 and both represented by 13.7 ± 11.22 and 8.8 ± 3.01 individuals, respectively.5. 2. 3. 2. In Farskour district:The seasonal abundance of the immature stages of the endoparasitoid E. citrina had the highest number in January for the first year, 2021 and February for the second year, 2022 in Farskour district. The annually average number of the immature stages of E. citrina was the highest during the first year, 2021 than the second year, 2022 and both represented by 14.9±15.75 and 4.3±1.82 individuals, respectively.5. 2. 4. Unknown mortality factors:5. 2. 4. 1. In New Damietta district: The population fluctuation of the total individuals and unknown mortality of the white date palm scale insect P. blanchardi during the two successive years (2021 and 2022) in New Damietta district. The insect had six peaks during the first year and seven peaks during the second year for each total individuals and unknown mortality. The highest peaks occurred in beginning of January, 2021 and Mid-December, 2022 for the unknown mortality and represented by 662 and 422 scales / 100 leaflets, respectively. The annually average number of the unknown mortality recorded the highest during the first year, 2021 than the second year, 2022 and both represented by 236.2 ± 180.18 and 199.4 ± 88.41 scales / 100 leaflets, respectively.5. 2. 4. 2. In Farskour district:The population fluctuation of the total individuals and unknown mortality of the white date palm scale insect P. blanchardi during the two successive years (2021 and 2022) in Farskour district. The insect had six peaks during the first year and five peaks during the second year for unknown mortality. The highest peaks occurred in beginning of January, 2021 and Mid-October, 2022 for the unknown mortality and represented by 520 and 430 scales / 100 leaflets, respectively. The annually average number of the unknown mortality recorded the highest during the first year, 2021 than the second year, 2022 and both represented by 215.3 ± 133.86 and 165.9 ± 119.25 scales / 100 leaflets, respectively. 5.3. The seasonal contribution by the different mortality factors in the total population mortality of P. blanchardi:According to the seasonal contribution caused by the ectoparasitoid, Aphytis spp. had the highest average number and its contribution in winter seasons during the two years (2021 and 2022) and also in the two districts New Damietta and Farskour. Meanwhile, summer seasons exhibited the lowest average number and its contribution during the two years and in the two districts. Regarding to the endoparasitoid Encarsia citrina recorded the highest average number and its contribution in winter seasons and the lowest average numbers and its contribution was in spring season during the first year, 2021 in New Damietta district. While, During the second year, 2022 in New Damietta district and during the two years (2021 and 2022) in Farskour district the lowest average number and its contribution was in autumn seasons. In respect to the predation recorded the highest average number and its contribution in winter seasons in the two years and in the two districts. While the lowest average number and its contribution in New Damietta was in spring during the first year, 2021 and in autumn during the second year, 2022 while, in Farskour was in spring during the two years.5.4. The annual contribution by the different mortality factors in the total population mortality of P. blanchardi:The unknown mortality factors had the highest average number and its contribution during the two years (2021 and 2022) in the two districts New Damietta and Farskour. Meanwhile, the lowest average number and its contribution was recorded by the predation during the first year, 2021 in the two districts while, the endoparasitoid E. citrina recorded the lowest average number and its contribution during the second year, 2022 in the two districts. 5. 5. Relationship between the host density and different mortality factors:The relationship between the host density and different mortality factors during the two years in the two districts were studied. Regarding to the predation, the correlation relationship was a positively significant during the first year, 2021 in New Damietta and Farskour districts. While, the correlation relationship during the second year, 2022 in New Damietta was negatively significant and in Farskour was non-significant. In respect to the ectoparasitoid Aphytis spp. and the endoparasitoid Encarsia citrina there were positively significant during the first year in the two districts and non-significant during the second year in the two districts.