Abstract
The bacterium Xylella fastidiosa (Xf) is an invasive insect-borne pathogen, which causes lethal diseases to important crops including olives, citrus, almonds and grapes as well as numerous forest, ornamental, and uncultivated plants. Outbreaks of Xf-related plant diseases are currently occurring in the Mediterranean region, causing substantial losses to various agricultural sectors. Several models have recently been published to identify which regions are at highest risk in Europe; however, such models did not consider the insect vectors, which constitute the key driver of short-range Xf spread. We fitted bioclimatic species distribution models to depict the macroclimatic preferences of the meadow spittlebug Philaenus spumarius L. (1978) (Hemiptera: Aphrophoridae), the major epidemiologically relevant vector currently responsible for Xf spread in the Europe. Many regions of Western Europe and Mediterranean basin are predicted by models as highly climatically suitable for this vector, including all regions where severe Xf have occurred so far. Conversely, the driest and warmest areas of the Mediterranean basin are predicted as little suitable for P. spumarius. Models forecast that agricultural-important parts of the southern Mediterranean area might experience a substantial decrease in climatic suitability for P. spumarius by the period 2040–2060. Areas predicted as highly suitable just for the bacterium but not optimal for this vector are apparently still free of severe Xf outbreaks, suggesting that climate tolerances of P. spumarius might partly explain the current spatial pattern of Xf outbreaks in Europe and should always be considered in further risk assessments.
Highlights
The bacterium Xylella fastidiosa (Xf) is an insect-borne plant pathogen that induces severe diseases in a wide array of ornamental and agricultural crops including Pierce’s disease of grapevines (PD), olive quick decline syndrome (OQDS), almond leaf scorch (ALS) and citrus variegated chlorosis (CVC) among others (Delbianco et al 2019)
Xf has only recently been officially detected in Europe, epidemiological data indicate that the Xf introduction is likely an older event in various Mediterranean areas (Soubeyrand et al 2018; Moralejo et al 2020), suggesting that the pathogen could be widespread in southern Europe and that outbreaks might occur in new areas if favorable ecological conditions are met
The present study aims at depicting the climate tolerances of P. spumarius, the main epidemiologically relevant vector involved in Xf spread in Europe
Summary
The bacterium Xylella fastidiosa (Xf) is an insect-borne plant pathogen that induces severe diseases in a wide array of ornamental and agricultural crops including Pierce’s disease of grapevines (PD), olive quick decline syndrome (OQDS), almond leaf scorch (ALS) and citrus variegated chlorosis (CVC) among others (Delbianco et al 2019). Xylella fastidiosa colonizes the xylem of plants and when the bacterial load is sufficiently large reduces xylem sap circulation. This disruption of water transport along xylem vessels causes decline in yield and fruit quality and may lead to the death of plants (Hopkins 1989). Native to Americas, Xf has invaded many regions including Asia, the Middle East and Europe (EFSA PLH Panel., 2019). In 2013, an OQDS outbreak reported in the Apulia region of South-Eastern Italy represented the first confirmed introduction and establishment of Xf in Europe (Saponari et al 2013). Since no efficient treatment exists to cure infected trees, control strategies implemented in the European Union mainly rely on pathogen early detection, removal of susceptible hosts in localities experiencing outbreaks, control of vectors and application of restrictive measures on planting material (EFSA PLH Panel., 2019)
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