Population and Mortality Studies on the Black Scale Insect, Parlatoria ziziphi (Lucas) (Hemiptera: Diaspididae) in an Egyptian Citrus Orchard

The diaspidid black scale, Parlatoria ziziphi (Lucas) is amongst the most destructive pests to citrus in several countries. This study was conducted in navel orange orchard at the experimental farm belonging to Mansoura University during 2017/2018 and 2018/2019. Parlatoria ziziphi had three peaks of abundance annually. The highest peaks occurred in autumn. The ectoparasitoid, Aphytis sp . had four peaks of abundance annually and its populations were synchronized with those of the insect. The endoparasitoid, H. aspidioti exhibited three-four peaks of abundance annually and the parasitoid populations were coincided partially with those of the insect. However, as the population of insect increased, the parasitism rates by Aphytis was significantly decreased, whereas those of H. aspidioti were unstable. Thus, Aphytis seems to be inverse-density mortality agent and its releases must be early in the season on low pest populations. Parasitism% by Aphytis sp. had two peaks annually, almost occurred in the period from May to August. Aphytis parasitism percentages ranged from 14.6 to 35.4%, whereas those of H. aspidioti ranged from 5.7 to 16.5% in both years. Harbolepis aspidioti recorded three peaks of parasitism in January, May, and August annually with the highest one was in January. Predation% in P. ziziphi populations ranged from 5.8 to 18.9%. The highest percentages of unknow mortality (12.3-17.8%) were in the period from December to January annually. The total population mortality ranged from 37.9 to 73.9%. Both parasitoid species contributed with the highest fate in the total population mortality of P. ziziphi in all seasons.