Physical Ripening Indices Improve the Assessment of Mechanical Harvesting Time for Olive Cultivars Resistant to Xylella fastidiosa subsp. pauca

Xylella fastidiosa subsp. pauca (Xfp) is a significant threat to Mediterranean agriculture, particularly impacting olive trees in southern Italy, causing Olive Quick Decline Syndrome. Resistant olive cultivars, such as 'Leccino' and 'Fs-17', have been identified as alternatives to restore the oliviculture within the infected areas. 'Frantoio' and 'Cipressino' are included in ongoing studies on genetic resistance to Xfp. The mechanization of olive harvesting is essential for reducing production costs in the olive oil sector. Two systems, trunk shakers and over-the-row machines, are used depending on the tree density and canopy structure, with super-high-density systems offering advantages in terms of cost and efficiency. This study investigates the feasibility of using simple and non-destructive indices to assess the optimal mechanical harvesting time. Different physical ripening indices, including detachment force, fresh weight, pigmentation, and firmness, were measured on four olive cultivars ('Fs-17', 'Leccino', 'Frantoio', 'Cipressino') in southern Italy over two years. The study found that the pigmentation index had a strong relationship with the detachment index, particularly for 'Fs-17', and 'Leccino', providing a reliable non-destructive measure for optimal harvesting time. The results indicate that the optimal harvesting times for mechanical harvesting are early September for 'Cipressino', early October for 'Fs-17', and mid-October for 'Frantoio' and 'Leccino'.