EFSA pest survey card on Xylella fastidiosa: how to characterise the host plant population?

EFSA developed the “Pest survey card on Xylella fastidiosa” for the preparation of surveys with the aim of guiding the Member States in gathering information needed for designing statistically sound and risk-based surveys for this pest. Characterising the host plant population targeted by surveys provides an answer to where to perform survey activities. This is a major challenge for surveillance of X. fastidiosa as it can be hosted by about 600 different plant species, growing throughout the EU territory in a variety of environments. For assisting surveyors in their preparatory tasks, the target population can be structured and subdivided in epidemiological units, in which the probability of infection by the bacterium is homogeneous. For this purpose, the “Host plant selection tool” built within the pest survey card provides guidance on the selection of host plants, allocating them in four categories of land use: agricultural, urban, forest and other areas. Rationales are also provided with the purpose of meeting the objectives of the surveys, such as the susceptibility of infection by multiple X. fastidiosa subspecies, the susceptibility of feeding by insect vectors, and the expression of symptoms, since some host species undergo an asymptomatic period. In addition, to prepare a risk-based survey, the target population can be subdivided based on the risk of introduction of X. fastidiosa in an area or on the risk of infection of some host plant species. The risk factors can be introduced in the survey design to better target the survey efforts. An accurate characterisation of the target population using the proposed methodology will help surveyors to design robust statistically sound and risk-based surveys for X. fastidiosa.