Population dynamics of the black scale, Parlatoria ziziphi (Lucas) on different citrus species in Damietta Governorate, Egypt

Field experiments were conducted in citrus orchard at kafr El-battikh reigon, Damietta Governorate, Egypt to evaluate the population density of the black scale, P. ziziphi on the different citrus plants as Mandarin, Lemon and Navel orange trees. Furthermore, the seasonal activity of P. ziziphi and the ectoparasitoid Aphytis spp during the two successive years (2021/22 and 2022/23).P. ziziphi reached the highest peak of abundance according to the alive individuals on Navel orange and Balady lemon trees in 3rd of November 2021with 414 and 321 indiv., during the first year 2021/22 respectively. During second year 2022/23, P. ziziphi reached the highest peak of abundance according to the alive individuals on Navel orange trees in 21st of October 2022 with 342 indiv.On the other hand Navel orange came in the first category with an average of 162.0 ± 21.06 and 150.6 ± 15.00 followed by Mandarin with 150.7 ± 16.22 and 140.3 ± 14.48 indiv. and Balady lemon with 135.6 ± 12.62 and 115.70 ± 10.66 indiv. during the two years with insignificantly differences at 5% level of the probability, respectively. The highest peak of Aphytis spp abundance reached 143 and 136 indiv. on Navel orange,129 and 129 indiv. on Mandarin and 117 and 103 indiv. on Balady lemon during during the two years 2021/22 and 2022/23, respectively. The ectoparasitism by Aphytis spp. exhibited the highest mortality factor for P. ziziphi on the three citrus trees while predation came in the second category with significant differences during the two study years.