Olive trees infected by a devastating bacterium can be identified before visible symptoms appear using a new, airborne remote-imaging method that scans entire orchards, reports a paper published online this week in Nature Plants. The scanning, which can be deployed using planes or drones, may help control the spread of infection and save southern Europe’s iconic tree.

Xylella fastidiosa is a devastating bacterium, transmitted by common sap-feeding insects, which causes various plant diseases. Olive trees are especially vulnerable, with the bacteria causing branches and twigs to wither, and leaves to appear scorched. Common in the Americas but only recently discovered in Europe, Xylella is spreading around the Mediterranean, with many orchards already destroyed in Italy’s olive-oil-producing Apulia region. As there is no cure, the only way to stop the disease’s progress is to cull infected trees, with earlier diagnoses being the key to more effective containment.

Pablo Zarco-Tejada and colleagues used special cameras, fitted aboard a small plane, to perform both hyperspectral (looking across the entire electromagnetic range) and thermal image analyses of orchards. The authors then tested olive trees on the ground for Xylella infection. They 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.