THE CURRENT STATUS OF XYLELLA FASTIDIOSA IN SALENTO (ITALY): ARE WE APPROACHING A NEW PHASE OF THE EPIDEMIC?

During these 10 years from the emergence of Xylella fastidiosa in olive trees in Salento, the destructive potential of its epidemic spread and the consequent dramatic impacts on several agroecosystem services, have been extensively documented. Main part of the territory of this peninsula has been included in the "demarcated infected area", where several containment measures are strongly recommended, and few are the mandatory (i.e. banning plantations of highly susceptible species). Such status coupled with favorable epidemiological conditions caused the persistence of the infections in the whole area, decimating millions of olive trees, the main crop and landscape species of the area. Most likely, the wide occurrence of deadly infections entails a reduction of the reservoirs of bacterial inoculum and infective insect vectors. Alongside, in the last couple of years an increasing number of occasional reports of symptoms remittance in trees not severely affected has been recorded, posing new complex questions to the scientific community. Initial investigations on recently isolated strains seem to exclude the insurgence of adaptive traits and loss of aggressiveness. While preliminary data on the evolution of the vector infectivity showed a decreasing trend; probably resulting in a reduction of the superinfections events on the surviving trees. New studies are therefore now necessary to understand the factors driving this new stage of the epidemic.