A number of new diseases of blueberry have been reported in the last four years, and some existing diseases have increased in importance. Emerging diseases may be caused by new pathogens, or by previously described, sometimes well-known pathogens that are increasing in incidence and severity. Examples of new or emerging diseases in the US include Blueberry necrotic ring blotch virus, blueberry bacterial scorch caused by Xylella fastidiosa, Exobasidium fruit and leaf spot caused by the fungus Exobasidium vaccinii, Valdensinia leaf spot of lowbush blueberry caused by the fungus Valdensinia heterodoxa, and Blueberry red ringspot virus. As blueberry production expands in the US and worldwide, disease incidence is being affected by changes in production practices, introduction of blueberries into new geographic areas, transmission via vegetative propagation from infected plants, and varying levels of resistance in new cultivars.