More than a million ancient olive trees in Southern Italy are being wiped out by Xylella fastidiosa, a deadly bacterial pathogen that has no known cure.
Xylella is endemic in parts of the Americas and has not been seen in Europe until 2013, when it was identified in Southern Italy. For many years, Xylella remained confined to the Americas. In 1994, it was noticed in Asia, in Taiwan causing leaf scorch on Asian pear. Then, Puglia was the first confirmed detection in Europe, followed by France in 2015. The introduction pathways of Xylella into Asia or Europe are unknown. However, it can be noted that Italy and France have intercepted several times Xylella on imported coffee plants from South America.
What is Xylella fastidiosa
From a taxonomic point of view, it is a complex species and several research studies have suggested that the different strains which are found on different host plants might be grouped into subspecies. Insects, like Cicadellidae and Cercopidaem, are known to be vectors of X. fastidiosa. It is thought that virtually all sucking insects are potential vectors of the bacterium. Symptoms vary according to the host plants but in general, as the bacterium invades xylem vessels and blocks the transport of water and soluble mineral nutrients, affected plants show drying, scorching, wilting of the foliage, eventually followed by plant death.
What’s happened in Italy
To fight the outbreak, the Italian government last year approved the felling of 3,000 trees in Salento, a southern region in the country’s heel, to create a sanitary buffer zone between affected and non-affected areas. For the tree growers, it was a double disaster as experts don’t know for sure the cause of Xylella. What they know is that Xylella does not harm humans but it can kill over 200 types of plant, including fruit trees and grape vines.
Under European Union rules, Italy is obliged to carry out a scientifically based containment plan to stop the disease from spreading to other EU countries. In addition to culling infected trees, this plan involves destroying healthy trees to create buffer zones. But, farmers supported by environmental activists who deplored the destruction of ancient trees, have protested against its implementation. Individual court rulings have found in their favor, stopping tree felling and the spraying of insecticide on their land.
Lost output has already had an impact on wholesale oil prices. A recent study in seven EU countries attributed a 20% hike over 2015 to the impact of the Xylella crisis. Now, olive growers are hoping that science will come up with a treatment for Xylella sooner rather than later.