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Remote Sensing and Spectroscopy in the race against deadly olive tree disease

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Xylella fastidiosa is a bacterium, considered by the European Commission as one of the most dangerous plant pathogens in the world. Native to the Americas, it was known for causing devastating infestations on vineyards and citrus trees. The bacterium is transported among trees by bugs which suck plant juices.

Once the bacteria enter the tree, they slowly colonize it and block transport of water, causing the tree to die of thirst. When Xylella first arrived in Europe, some time before 2013, it ravaged hundreds of square kilometres of ancient olive groves in the south of Italy, and it has since been found in Spain and France.

There is no known remedy for the infestation- the only measure is to diagnose it and burn the plant to prevent the bacteria from spreading. However, infestation may be present in a tree for a long time without any visible signs, and that makes it even more difficult to contain the disease.

Image credit: REUTERS/Tony Gentile

In a recent publication, researchers resort to remote sensing to assist early diagnosis and containment of the infestations. They mount two cameras on drones or aircraft: one thermal, and one hyperspectral.

They combine high-resolution fluorescence, thermal stress indicators and spectral signatures of characteristic plant traits and obtain 80% accuracy in detecting the disease, even when infected trees are visually asymptomatic.

The technique can be used on a landscape scale, as the airborne sensors can scan large areas faster than human inspectors on the ground. At the same time, scientists are testing cultivars resistant to the infection. As restoration of an ancient olive grove does not happen overnight, timely detection is crucial for the eradication of the disease.

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