Outbreak of Xylella fastidiosa subsp. pauca ST53 affecting wild and cultivated olive trees on the island of Mallorca, Spain

The Balearic Islands have emerged as a hotspot for the invasive plant pathogen Xylella fastidiosa (Xf). Since 2016, the Xf subsp. fastidiosa and multiplex have been detected causing almond leaf scorch and Pierce’s disease on the island of Mallorca, Spain, and a new sequence type (ST), ST80, of subsp. pauca is infecting wild and cultivated olive trees on the island of Ibiza. In addition, Xf subsp. multiplex ST81 is widespread in scrublands, and causes mild, sub-lethal dieback of wild olive trees in Menorca and Mallorca. A new outbreak is here reported of the Xf subsp. pauca in the municipality of Sencelles in the centre of Mallorca island. In early 2024, dying patches were observed in wild olive trees (Olea europaea var. europaea subsp. sylvestris). Samples from these trees were Xf-positive in different qPCR tests, and the pathogen was subsequently identified as belonging to ST53 of subsp. pauca, the same genetic variant responsible for olive quick decline syndrome in Apulia, Italy. More than 184 plants of eight hosts have tested positive for subsp. pauca within a demarcation zone of approx. 1 km radius. The identified host species include 124 wild olive trees, 40 cultivated olive trees, nine Rhamnus alaternus, six Nerium oleander, two Lavandula angustifolia, one Laurus nobilis, one Lavandula dentata and one Polygala myrtifolia. Of particular concern is detection of co-infections by Xf subsp. subsp. pauca and multiplex on plants from natural settings (wild olives, L. dentata and R. alaternus), posing potential risk of genetic recombinations. Intensive surveys are being carried out to contain the spread of ST53, and infected plants have been destroyed in the demarcated zone.