Exploring scale insects biodiversity in orange orchards: insights from Guelma province, Algeria

Abstract

Scale insects are pests affecting citrus crops in the Mediterranean basin, but their significance is often overlooked in some countries due to insufficient information about the threat they pose to this type of cultivation. In Algeria, various studies have aimed to identify and highlight the most harmful species impacting citrus orchards. This research specifically focuses on compiling a list of species affecting orange orchards in three regions of Guelma province (northeast Algeria) which are Boumahra Ahmad, El Fedjoudj and Guelma. Branch samples with their leaves were collected from all cardinal directions of the trees as well as from the center of the canopy during the winter-spring period from 2014 to 2018 while examining the climatic influence on their presence. Seventeen species were identified, with Aonidiella aurantii (Maskell, 1879), Parlatoria ziziphi (Lucas, 1853) and Coccus pseudomagnoliarum (Kuwana, 1914) being dominant and Lepidosaphes beckii (Newman, 1869), Saissetia oleae (Olivier, 1791) and Saissetia coffeae (Walker, 1852) considered rare. Non-parametric richness estimators (Chao 1, Chao 2, Jack 1 and Boot) suggest the potential presence of additional species, reaching 20.15 ± 0.96, indicating that the count may extend to 21 scale insects in the surveyed orchards. Spearman correlation analysis applied to species and climatic conditions reveals their influence on species abundance, but not on their diversity. We observed a positive impact on relative humidity and a negative impact on average temperature.