Update of the Scientific Opinion on the risks to plant health posed by Xylella fastidiosa in the EU territory

Abstract

EFSA was asked to update the 2015 EFSA risk assessment on Xylella fastidiosa for the territory of the EU. In particular, EFSA was asked to focus on potential establishment, short-and long-range spread, the length of the asymptomatic period, the impact of X. fastidiosa and an update on risk reduction options. EFSA was asked to take into account the different subspecies and Sequence Types of X. fastidiosa. This was attempted throughout the scientific opinion but several issues with data availability meant that this could only be partially achieved. Models for risk of establishment showed most of the EU territory may be potentially suitable for X. fastidiosa although southern EU is most at risk. Differences in estimated areas of potential establishment were evident among X. fastidiosa subspecies, particularly X. fastidiosa subsp. multiplex which demonstrated areas of potential establishment further north in the EU. The model of establishment could be used to develop targeted surveys by Member States. The asymptomatic period of X. fastidiosa varied significantly for different host and pathogen subspecies combinations, for example from a median of approximately 1 month in ornamental plants and up to 10 months in olive, for pauca. This variable and long asymptomatic period is a considerable limitation to successful detection and control, particularly where surveillance is based on visual inspection. Modelling suggested that local eradication (e.g. within orchards) is possible, providing sampling intensity is sufficient for early detection and effective control measures are implemented swiftly (e.g. within 30 days). Modelling of long-range spread (e.g. regional scale) demonstrated the important role of long-range dispersal and the need to better understand this. Reducing buffer zone width in both containment and eradication scenarios increased the area infected. Intensive surveillance for early detection, and consequent plant removal, of new outbreaks is crucial for both successful eradication and containment at the regional scale, in addition to effective vector control. The assessment of impacts indicated that almond and Citrus spp. were at lower impact on yield compared to olive. Although the lowest impact was estimated for grapevine, and the highest for olive, this was based on several assumptions including that the assessment considered only Philaenus spumarius as a vector. If other xylem-feeding insects act as vectors the impact could be different. Since the Scientific Opinion published in 2015, there are still no risk reduction options that can remove the bacterium from the plant in open field conditions. Short-and long-range spread modelling showed that an early detection and rapid application of phytosanitary measures, consisting among others of plant removal and vector control, are essential to prevent further spread of the pathogen to new areas. Further data collection will allow a reduction in uncertainty and facilitate more tailored and effective control given the intraspecific diversity of X. fastidiosa an...

Effectiveness of in planta control measures for Xylella fastidiosa

“…Physical treatments (such as hot water treatments), agricultural practices (such as pruning), plant breeding (e.g. use of resistant varieties and GM plants) and vectors control are excluded from this review as they are included in the updated pest risk assessment for X. fastidiosa (EFSA PLH Panel, 2019). The use of antibiotics is not considered in this review due to the risk of antimicrobial resistance development.…”

Pest survey card on Xylella fastidiosa

“…In the initial phase of disease spread (0-2 years), the rate of increase is negligible but accelerates after the second year. For example, it was shown that under a scenario of high plant susceptibility and high vector population density, these spread rates lead to maximum spread distances (distance from the first inoculated plants) of up to 1.5 km in 5 years (EFSA PLH Panel, 2019a). After year 5, the rate of spread of the disease is 0.65 km per year (EFSA PLH Panel, 2019a).…”

“…Additionally, the studies reviewed were all reporting results of experiments done with relatively young plants with artificial inoculation under controlled conditions and, thus, might not have the same results in field conditions. Median duration of the asymptomatic period for different host plants and Xylella fastidiosa subspecies derived from survival analysis(EFSA PLH Panel, 2019a) vi.…”

Report on the methodology applied by EFSA to provide a quantitative assessment of pest‐related criteria required to rank candidate priority pests as defined by Regulation (EU) 2016/2031

“…In order to connect the different outputs and harmonise their content, the different EFSA WGs planned to synchronise their outputs, whenever possible. In case of Xylella fastidiosa , the assessment was performed as part of the activity of the WG dedicated to the ‘Update of the Scientific Opinion on the risks to plant health posed by X. fastidiosa in the EU territory’ (EFSA PLH Panel, ).…”