Vie d'ingresso dei patogeni forestali esotici

Human-driven species expansion has increased tremendously in the last century, as a consequence of the unprecedented growth of international travel and trade, resulting in huge disturbance to ecosystems and severe socio-economic impact. In plants, emerging infectious diseases (EIDs) are linked to biological invasions. More than half of the world plant EIDs in the last few decades have resulted from the arrival of previously unrecognized pathogens. Many studies confirm that the main pathway of entrance of pathogens was the trade of living plants. In particular, the trade of ornamental woody plants plays a role of primary concern. These observations should serve to focus attention on the risk inherent in the trade of ornamental plants for planting in soil. This pathway is particularly insidious as invasive harmful organisms are not easily detectable in soil, and they are, in addition, almost unknown and neglected in their native ranges. Global trade has given the opportunity to pathogenic microorganisms that have remained geographically isolated to spread far beyond their natural range and to hybridize with related species. This process brought to the birth of new organisms with different/wider host range of those of the parental species. The global use of forest plantations with exotic tree species, using one or few clones of the same species planted in huge areas and intensively managed, has increased the risk of attacks by insects and pathogens, which are introduced accidentally and/or have adapted to new host trees. Lastly climate change enhances the aggressiveness of some pathogens and, on the other hand, stresses the native flora, making it more prone to attacks by pathogens. Everyday hundreds of pathogens are at European borders ready to spread; Europe should devote more efforts to research for detecting them more accurately and improve its own legislation in order to prevent the establishment of new alien pests and pathogens.