Spittlebugs as vectors of Xylella fastidiosa in olive orchards in Italy

Daniele Cornara,Adam R Zeilinger,Giuliana Loconsole,Angelo De Stradis,Giovanni P Martelli,Donato Boscia,Domenico Bosco,Rodrigo P P Almeida,Francesco Porcelli,Maria Saponari

doi:10.1007/s10340-016-0793-0

Abstract

The recent introduction of Xylella fastidiosa in Europe and its involvement in the Olive Quick Decline Syndrome (OQDS) in Apulia (Salento, Lecce district, South Italy) led us to investigate the biology and transmission ability of the meadow spittlebug, Philaenus spumarius, which was recently demonstrated to transmit X. fastidiosa to periwinkle plants. Four xylem-sap-feeding insect species were found within and bordering olive orchards across Salento during a survey carried out from October 2013 to December 2014: P. spumarius was the most abundant species on non-olive vegetation in olive orchards as well as on olive foliage and was the only species that consistently tested positive for the presence of X. fastidiosa using real-time PCR. P. spumarius, whose nymphs develop within spittle on weeds during the spring, are likely to move from weeds beneath olive trees to olive canopy during the dry period (May to October 2014). The first X. fastidiosa-infective P. spumarius were collected in May from olive canopy: all the individuals previously collected on weeds tested negative for the bacterium. Experiments demonstrated that P. spumarius transmitted X. fastidiosa from infected to uninfected olive plants. Moreover, P. spumarius acquired X. fastidiosa from several host plant species in the field, with the highest acquisition rate from olive, polygala and acacia. Scanning electron microscopy (SEM) revealed bacterial cells resembling X. fastidiosa in the foreguts of adult P. spumarius. The data presented here are essential to plan an effective IPM strategy and limit further spread of the fastidious bacterium.

Highlights

Human activities, especially the speed and volume of transportation, have accelerated the global expansion of invasive species because of a breakdown of natural barriersJ Pest Sci (2017) 90:521–530 to dispersal, so much so that the distribution of invasive species appears to be restricted primarily by climatic factors (Capinha et al 2013)
From October 2013 to December 2014, the spittlebug population on olive plants was almost exclusively composed of P. spumarius (98.56 % of the overall spittlebug population collected from olive plants); N. campestris (1.44 % of the overall spittlebug population) was rare
1 out of about 200 N. campestris that had been collected in July 2014 tested positive for X. fastidiosa; the single individual positive for the bacterium was collected on an oleander plant

Summary

Introduction

Especially the speed and volume of transportation, have accelerated the global expansion of invasive species because of a breakdown of natural barriersJ Pest Sci (2017) 90:521–530 to dispersal, so much so that the distribution of invasive species appears to be restricted primarily by climatic factors (Capinha et al 2013). One activity highly impacted by invasive species is agriculture, where crop diversity has become gradually more homogeneous at the global scale (Khoury et al 2014), leading to a suite of shared pests and diseases. It is not surprising that some of the major current and future challenges to agriculture gravitate around the potential risks associated with the introduction of invasive species into new regions where they are absent. The recent establishment of the vector-borne bacterium Xylella fastidiosa in the Salento peninsula (southern Italy) (Saponari et al 2013) highlights the risks associated with the unintended introduction of organisms into new regions. Because X. fastidiosa vectors are present throughout the Mediterranean basin (EFSA 2015), and this bacterium colonizes several crop species of economic and cultural importance (e.g., grapevine, citrus, almond) (Hill and Purcell 1997), the threat due to its introduction to Europe is significant

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