In 2008, an unwelcome visitor arrived in Italy, specifically in the region of Apulia. It traveled on a coffee plant and then continued to spread as it infected and killed millions of olive trees in ever-widening circles. This visitor is called Xylella and it’s a bacterium.
The first withered olive trees appeared near Gallipoli. Bunches of leaves turned brown and crunchy around the edges. Then, whole groves started to decline. Farmers whose families had tended olives for generations watched their trees dry up and their businesses plummet.
At first, it wasn’t clear what was causing the decline. Was it a fungus? A virus? Scientists tried urgently to find the cause. It became a race against time.
One researcher from a local agricultural institute had just come back from a conference in California, where he’d learned about the plant bacterium Xylella fastidiosa. The symptoms the olive growers were seeing, he realized, looked exactly like what seen in the talks he’d attended. Sure enough, when he and his colleagues tested the Italian trees, they found the bacterium lurking in their woody hearts.
This was not good news. The European Commission considers Xylella to be among the most dangerous plant bacteria in the world. Different strains of it have destroyed vineyards in California and citrus trees in Brazil, killing acres of valuable plants and causing billions in lost revenue.
Xylella causes plants to die of thirst from the inside out. The bacteria get passed from tree to tree by tiny pests called spittlebugs. The bugs are native to the region, and before Xylella arrived on Italian shores, they weren’t seen as a problem. Now, their presence causes terror in the farmers whose olive groves are being decimated.
Until the olive trees fell ill, Xylella had never been seen in Europe, and its identification in Italy set off alarm bells across the scientific and political communities of the European Union. Italian olive growers produce 15 percent of the world’s virgin olive oil, worth more than $2 billion each year. Spain produces even more. Anything that threatened the trees threatened the entire European economy.
Olives are also central to the identity of the region. There are over 60 million trees in Puglia alone, which—until recently—produced about 40 percent of all the olive oil Italy exports. Nearly half a million trees are the beloved “ulivi secolari,” centuries-old trees whose gnarled trunks have stood majestically even as vast changes swept across the region.
But the arrival of Xylella threatens the traditional order and the groves worth billions of dollars. Scientists and some growers have been working feverishly to figure out what, exactly, is going on and whether they can mitigate the damage.
Now there’s good news. Seven years after deploying a protocol combining organic treatments with a series of other agricultural practices, treated olive groves demonstrate resilience to Xylella fastidiosa. In Puglia, which has been ground zero for the country’s devastating Xylella fastidiosa epidemic, dozens of groves remain as productive as ever.
The results of the protocol’s deployment were presented at the 14th International Conference on Plant Pathogenic Bacteria in Assisi by the researchers who study the spread of the deadly olive tree bacteria. The protocol is working. “When correctly deployed, it provides safe prevention, a shield against the effects of Xylella,” Marco Scortichini, the lead researcher for olives and fruit crops at the Italian Council for Agricultural Research and Economics, told Olive Oil Times.
Scortichini and other researchers published two studies in the Phytopathologia Mediterranea and Pathogens scientific journals in 2018 and 2021, demonstrating the results of the control strategy adopted in Apulia.
“With this protocol, Xylella becomes for the olive tree what downy mildew is for vines,” Scortichini said. “For the containment to work, you need to deploy the treatment every year and every month between March and September.” He added, “By developing the protocol, the goal was not to eradicate Xylella, as it is an unfeasible goal, but to control it similarly to other plant diseases.”
But the treatment is expensive, Francesco Paolo D’Urso, owner of Masseria Curtimaggi, a two-time NYIOOC award winner, told Olive Oil Times. “Every year since then, I have to proceed to treat my trees several times, and the organic product by itself costs me between €35,000 and €40,000 – €150 to €160 per hectare – which means it considerably reduces our final income,” a grower said. Small growers cannot afford it.
But as the growers continued to see their trees—as well as their income—dying, more and more of them adopted the protocol. An unintended benefit was that the anti-xylella protocol proved effective against other pests as well—like the devastating olive fruit fly. Now more and more olive groves are starting to regain their health and growers their hope of a return to normal.
Discussion about this post