Effect of physico-chemical properties of some pomegranate varieties from Tunisia on the infestation of fruits by Ectomyelois ceratoniae Zeller (Pyralidae) and Deudorix (Virachola) livia Klug (Lycaenidae)

Abstract

Ectomyelois ceratoniae and Deudorix livia are the main pests of pomegranate Punica granatum L. in Tunisia. This study was carried out to investigate the susceptibility of five Tunisian pomegranate varieties (Tounsi, Guebsi, Gares, Zehri, and Baldi) from two oases (Gafsa and Degache) to infestation by E. ceratoniae and D. livia during fruit ripening. To this end, the physico-chemical properties of these pomegranate varieties were quantified during the ripening period and correlated with insect infestation. The results showed that all varieties were infested by E. ceratoniae and D. livia and that the severity of the infestation depended strongly on the pomegranate variety and the ripening stage of the fruit. It was observed that the infestation caused by E. ceratoniae was early as compared to D. livia on all the pomegranate varieties at two oases conditions. Moreover, results showed that biochemical and physico-chemical properties changed during fruit maturity. The total soluble solids (TSS), sugars, maturity index, fruit peel water content, and fruit weight are significantly increased but the titratable acidity and peel hardness are significantly decreased with ripening stage. The results pointed out that pomegranate infestation varied depending on the morphological changes of the fruit. In addition, a significant correlation was observed between E. ceratoniae and D. livia infestation and fruit juices TSS (r = 0.36 and r = 0.68), maturity index (r = 0.44 and r = 0.35), and total sugar (r = 0.36 and r = 0.67). Analyses also revealed a high negative correlation between fruit peel hardness and D. livia infestation (−0.63). The findings of this research will enhance comprehension regarding the behavior of D. livia and E. ceratoniae, which infest various pomegranate cultivars in Tunisian oases. Consequently, this will facilitate the refinement and implementation of management approaches aimed at addressing both species. For instance, early harvesting of fruits at the onset of ripening, prior to pest activity can significantly reduce levels of pomegranate infestation.