Drones equipped with hyperspectral and thermal sensors will be deployed in Italy to spot trees infected with Xylella fastidiosa, the deadly bacterium that has been devastating the country鈥檚 olive crops for almost a decade.
The sensors will be able to detect almost indiscernible signs of early infection, such as very slight changes in colour to the leaves, allowing farmers to cull affected trees and prevent outbreaks. More than 300,000 trees will be examined using the new drone technology in the next few months.
鈥淭his technology has the potential to give the Italian government a major advantage in the fight against Xylella,鈥� says Manuela Matarrese at DTA, a research consortium involved in the project. 鈥淲e tend to realise far too late if a plant is infected 鈥� these drone sensors will allow us to spot and prevent outbreaks rather than just react to them.鈥�
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Early detection strategies like this are key for reining in Xylella, which is spread by spittlebugs that feed on infected plants, ingesting bacteria and passing them to healthy plants nearby. Once the bacteria have infected a plant, they block the xylem vessels that transport water through the plant, cutting off its ability to absorb water and, eventually, killing it.
鈥�Xylella is particularly dangerous because it has many different natural hosts through which it can spread,鈥� says , a plant health expert at the European Food Safety Authority in Italy. 鈥淭here are hundreds of different plant species that can host it.鈥�
The first olive tree became infected in Italy in 2013, in the region of Puglia, on the southern edge of the country. Researchers now believe the bacterium arrived via ornamental coffee plants that entered Europe from abroad. Within two years, it had spread so rapidly that it threatened to destroy the entire region鈥檚 livelihood. Millions of olive trees died and thousands more had to be culled to prevent further spread.
鈥淭his is why it鈥檚 so important not to take or bring plants back with you when you travel,鈥� says Maiorano.
Xylella infection, also known as Pierce鈥檚 disease, has now been detected in Corsica, mainland France, Spain and Portugal. It is estimated that it could end up costing the European Union up to in lost crops.
In Puglia, which produces 40 per cent of Italy鈥檚 olive oil, the impact has been devastating. Much of the southern part of the region has already lost the battle against the bacterium, with entire plantations wiped out 鈥� some of which were home to olive trees more than 1000 years old. The .
Efforts are now concentrated on preventing the spread to the north of the region, where infections remain rare thanks to a strict containment strategy.
Under national legislation, as soon as a tree is found to be infected with Xylella, it must immediately be cut down 鈥� along with all vulnerable species within a 50-metre radius. A 2.5-kilometre zone around the infected plant is then closely monitored to prevent spread to surrounding trees. The remote-detection drones will ensure that any infected tree in these areas is diagnosed and culled quicker than ever before.
The hope is that this ruthless containment strategy in infected regions can buy time for the rest of the country鈥檚 olive plantations until a cure can be found.
Meanwhile, people are developing plant varieties that are resistant to infection. A variety of olive tree known as FS17, developed by the Italian National Research Council, is proving to be resistant to the bacterium, earning the nickname 听贵补惫辞濒辞蝉补 (fabulous) among Italian farmers. It is only the second olive tree variety, alongside the historic Leccino variety, considered resistant enough to Xylella to be allowed to be planted in infected regions.
There is also research on treatments based on viruses that infect bacteria, called bacteriophages. A team at Texas A&M AgriLife in the US has developed a that can be injected into infected trees, effectively killing the bacteria without harming the plant.
But these possible solutions are still in the early stages. For now, containment is the best tool that farmers and governments have at their disposal to control the disease.
, the head of agriculture of the regional government in Puglia, says the new early detection strategies are key. He hopes the high costs paid in his region over the past decade can serve as a lesson for others in Italy and around Europe.
鈥淎s soon as you spot a case of the disease, you must act right away to eradicate it,鈥� he says. 鈥淚n Puglia, this quick intervention didn鈥檛 happen at first. And if you wait even a little bit, it鈥檚 already too late.鈥�
