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.