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Research finds that a remote type of imag­ing method can scan orchards and pin­point olive trees infected with a dan­ger­ous bac­terium before symp­toms appear. The scan, which is put in a drone or plane, has spe­cial cam­eras that iden­tify sub­tle changes in leaf color that aren’t detectable to the naked eye. It could be a sig­nif­i­cant help in stem­ming the spread of infec­tion and sav­ing iconic trees in south­ern Europe.

Xylella fas­tidiosa (Xf) is a dan­ger­ous bac­terium that can cause dis­ease in more than 350 plants. The pathogen has infected elm, oak, sycamore, almond and cit­rus trees, but olive trees are par­tic­u­larly sus­cep­ti­ble. Signs in infected olive trees include leaves that appear scorched, along with with­ered branches and twigs.

While Xf has long plagued the Amer­i­cas, in recent years, it has spread to Asia and Euro­pean coun­tries bor­der­ing the Mediter­ranean Sea. It’s respon­si­ble for the destruc­tion of many olive orchards in the Apu­lia region of Italy.

The pathogen has no cure. Culling infected trees is the only way to stop the spread to healthy trees. The prob­lem is that once trees are infected, they may show no symp­toms for up to a year, dur­ing which time com­mon sap-feed­ing insects may be trans­mit­ting the infec­tion. There­fore, early detec­tion is vitally impor­tant for its erad­i­ca­tion.

In the study, Pablo Zarco-Tejada of the Euro­pean Com­mis­sion worked with experts from Swansea Uni­ver­sity and other Euro­pean insti­tu­tions. They put the cam­eras onboard a small plane to take images of orchards and after­ward tested the olive trees for infec­tion with Xf.

“Our study found that the effects of the bac­te­r­ial infec­tion can be remotely detected before any vis­i­ble symp­toms appear, allow­ing for rapid and accu­rate map­ping of Xylella-infected olive trees across tar­get orchards,” said co-author Peter North.

“The spread of plant dis­eases is pre­dicted to become an increas­ing prob­lem with cli­mate change, includ­ing for the UK. Inter­na­tional coop­er­a­tion is essen­tial for early detec­tion, to con­trol dam­age and pre­vent spread. This study demon­strates the pos­si­bil­ity of detec­tion of symp­toms at an early stage, and may be adapted to drones and air­craft for wide­spread use,” said coau­thor Rocio Her­nan­dez-Clemente.

As the air­borne scan iden­ti­fied infected olive trees with greater than 80-per­cent accu­racy, it promises to be a valu­able aid in help­ing other plants affected by Xf. Because the pathogen is viewed as a pro­found threat to plants around the world, the dis­cov­ery of the novel tech­nique is most wel­come news to olive grow­ers and other seg­ments of the agri­cul­ture indus­try. Plans are in the works to try the scan on almond groves in Spain and vine­yards in Mal­lorca soon.

The study was pub­lished in the jour­nal Nature Plants.

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