Statement of EFSA on host plants, entry and spread pathways and risk reduction options for Xylella fastidiosa Wells et al.

Abstract

Following a request from the European Commission, EFSA was asked to provide urgent scientific and technical assistance on the plant pathogenic bacterium Xylella fastidiosa. X. fastidiosa was detected in olive trees in Lecce province in Apulia, Italy, in October 2013. This is the first outbreak of X. fastidiosa under field conditions in the European Union. EFSA reviewed the host range and vectors, the pathways for entry and spread and the risk reduction options. Known hosts include many cultivated and spontaneous plants common in Europe, however a range of European wild plant species would meet this bacterium for the first time, increasing uncertainty on the host range. All xylem-fluid feeding insects in Europe should be regarded as potential vectors of X. fastidiosa and identification of the vector in the Apulian outbreak is pending. The main entry pathway for X. fastidiosa is the movement of plants for planting. Infective vectors of X. fastidiosa transported on plant consignments are also of concern. The only route for natural spread of X. fastidiosa is by insect vectors that generally fly short distances up to 100 metres, but can be transported by wind over long distance. The movement of infected plants for planting is the most efficient way for long-distance dispersal of X. fastidiosa. There is no record of successful eradication of X. fastidiosa once established outdoors due to the broad host range of the pathogen and of its vectors. Strategies for prevention of introduction from areas where the pathogen is present and for containment of outbreak should focus on the two main pathways and be based on integrated system approach combining, when applicable, the most effective options.

Experimental Nets for a Protection System against the Vectors of Xylella fastidiosa Wells et al.

“…Saponari et al [5] demonstrated that olive trees with leaf scorch symptoms (i.e., branches with basal and apical pale green leaves, later expressing different degrees of scorching starting at the leaf tips, partial defoliation, and death of shoots and branches) were positive for Xylella fastidiosa Wells et al subspecies pauca, sequence type (ST) 53 (Xanthomonadales, Xanthomonadaceae) [6]. This study was the first widespread detection of this bacterium in Europe, and a quarantine around the infected area was imposed [7]. Unfortunately, quarantine was not able to limit the diffusion of the bacterium and, by the end of 2013, the affected area had grown to almost the entire Salento Peninsula.…”

«Hands off the olive trees!»: the epistemic war in the Xylella fastidiosa epidemic in Italy. A Computer-Assisted Text Analysis of User-generated content on social media

“…In October 2013, analyses conducted by Boscia's team demonstrated that the disease -named «Olive Quick Decline Syndrome» (OQDS) -was indisputably associated with the presence of X. DNA on all the diseased plants. Within a month, the Regional Council of Apulia issued an emergency plan (Regione-Puglia Dgr 2023/2013), approved by the European Food Safety Authority (Efsa 2013): since there was (and still is) no cure, the only possible options to prevent an outbreak were pruning, eradication of trees with symptoms, and use of chemical treatments against vector insects (Saponari et alii 2014).…”

Xylella fastidiosa, Possible New Threat to Chestnut (Castanea sativa Mill.) in Italy

“…Xylella fastidiosa is a polyphagous bacterium and it has been detected in 679 host species [7], but does not cause disease in most of these [8]. In 2013, it was already known that Xf (regardless of subspecies) had 132 host species belonging to 46 different families [9]. In 2016, the number of host species discovered had already risen to 329, belonging to 75 different families, and in 2018 it reached 563 species from 82 different botanical families [10].…”