Hot water treatment of Vitis sp. for Xylella fastidiosa

Following a request from the European Commission, the EFSA Panel on Plant Health (PLH) reviewed Italian technical guidelines and the ANSES (Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail) opinion on the use of hot water treatment (HWT) on Vitis sp. planting material, assessing its efficacy in the elimination of the xylem-invading bacterial pathogen, Xylella fastidiosa. HWT is a robust and reliable technique used to destroy life stages of pests (insects, nematodes) and to inactivate pathogens (phytoplasma, bacteria, fungi) in dormant plant propagation materials (grapevine and other crops). An effective HWT sanitizes the planting material without affecting plant survival and development. For grapevine, HWT to eliminate the Grapevine flavescence dorée phytoplasma (FD) from planting materials is among the special requirements for the introduction and movement of Vitis sp. to protected zones in the EU. The conditions of 50°C for 45 min, prescribed and recommended to sanitize grapevine planting material against FD, are considered by the Panel to be also effective against X. fastidiosa and its subspecies. Despite uncertainties on variable thermotolerances of the bacteria, a HWT treatment of 50°C for 45 minutes can effectively account for different thermotolerances. It should be noted that the quality of the HWT is subject to the proper application of the operating procedures to guarantee vigorous growth and pathogen freedom of planting material.