It looks as though there is no resolution in sight. Scientists at the University of Bari have established that Xylella does indeed cause leaf scorching syndrome (though some cultivars are more susceptible than others). Meanwhile the EU has reiterated that the measures ordered last year for the Salento were appropriate, namely the uprooting of infected trees and widespread use of pesticides in a 20 km strip north of the infected zone (that zone has itself shifted northward as the bacteria spreads). Meanwhile politicians in Puglia who halted the earlier measures convened an international roundtable of scientists (also significantly in Bari, a challenge indeed to the authority of the group referred to above) who reiterated the alternative strategy of attempting to heal the trees (and the soil). Specifically measures are being taken to employ the region’s organic waste as compost for the olive groves and so nourish soil rendered sterile by a half century of herbicide use. Already growers are being fined for not mowing their groves (and so providing an environment favorable to the spittle bugs that carry Xylella). Nature magazine has reported on the syndrome, basically supporting the EU approach. Overlooked in much of this discussion is whether trees can recover from the scorching syndrome: Nature describes Xylella as fatal to olive trees. There are indications instead that trees can recover if properly cared for, while a French research consortium has developed a milk-based chemical product which it claims can kill Xylella bacteria. So the question remains: radical uprooting and pesticide use (which many claim will in any case not halt the spread of Xylella) or learning to live with the bacteria while healing the trees through best (organic) practices and the search for tree-specific non-invasive remedies.
I'm busy working on my blog posts. Watch this space!