Aerial Scan May Identify and Save Infected Olive Trees

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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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