In Apulia, Italy’s boot heel, the olive tree is sovereign.
“Olive trees pretty much cover the entire province,” says Rodrigo Almeida, an associate professor in Berkeley’s Department of Environmental Science, Policy and Management. “The olive tree defines Apulia’s identify. The people have a deep emotional connection to their trees. Families plant them to mark the births of their children. They cherish them.”
Sadly, the cherished trees may be going the way of the dodo bird – or at least, the American chestnut. “Young trees, the ancient centennial trees, they’re all dying,” says Almeida. “The loss is massive.”
They’re perishing by the thousands, done in by a bacterium known as Xylella fastidiosa, a pathogen that can infect a wide variety of plants, including olives. Further, the rate of the die-off is accelerating, and the vast number of Apulia’s trees is no insurance against their ultimate extirpation. Back to the American chestnut: The mighty mast-producing deciduous trees once constituted a quarter of the forest cover in eastern North America. Today, they’re virtually extinct in their original range, wiped out by a blight that hitched into the U.S. on Japanese Chestnut trees imported by a New York nurseryman in 1876.
As with the chestnut blight, Apulia’s epidemic also can be attributed to imported plants: X. fastidosa-infected coffee trees shipped in from Costa Rica seem the most likely culprits. The first affected olive trees were noted near the town of Gallipoli in 2013; now, three years later, the entire province is a hot zone.
X. Fastidosa can be eradicated if the initial area of infection is small and circumscribed and early and aggressive actions are taken. Affected trees must be destroyed. Pesticides must also be used, often heavily, to kill the disease’s vectors, small sap-sucking insects such as sharpshooters and spittlebugs. Similar measures are used in California to control Pierce’s Disease, an X. fastidiosa variant that attacks grapevines and is spread by at least two sharpshooter species.
If Apulian authorities had responded forcefully to the initial Xylella outbreak, Almeida argues, they might have scotched the epidemic. And in fact, Italy was required, under European Commission protocols, to institute rigorous measures including pesticide applications. But the EC measures were never implemented due to local resistance, and environmentalists and allied politicians have sued to block all attempts at Xylella control. Indeed, resistance to EC diktats has swelled into a social movement that has engulfed all of Italy, evoking the recent Brexit brouhaha.
Meanwhile, France, which also has some hotspots of X. fastidiosa (albeit of a different genotype than the bacterium found in Italy), has instituted the mandated EC measures, and appears to have contained the pathogen.
Almeida is sympathetic to Apulian resistance, where control measures would include cutting infected but asymptomatic trees. As he wrote in Science in July, “…The EC aims to address the threats of X. fastidiosa as a plant pathogen, demanding management and containment measures. But the reality to Apulians is different: Cutting down their olive trees means destroying the physical embodiment of their families and history.”
Further complicating any attempt at an effective response is rising conspiracist sentiment. For Italy, Xylella is the equivalent of America’s black helicopters and chemtrails.
“There is a degree of harmony in Europe’s scientific community on what must be done, but the distrust of science and scientists is growing in Italy,” says Almeida. “We’ve raised the alarms, but very little is being accomplished on the ground.”
An important lesson from the Apulia’s experience, Almeida says, is that future containment strategies must go beyond technical solutions and take into account social and cultural factors. He concludes his piece in Science with a frank assessment of the challenge. “Rapid reaction time is key to success in managing outbreaks, unfortunately building trust among stakeholders to solve environmental problems often requires years.”
Unhappily for Southern Italy and olive oil lovers everywhere, Almeida says it’s too late for eradicating Xylella in Apulia. The only question now is how far it will spread, and how fast.