A diagnostic guide for oak wilt disease in oak and chestnut

Oak wilt, caused by the ascomycete fungus Bretziella fagacearum, is a deadly vascular disease impacting numerous Fagaceae hosts, including important forest, urban landscape, and orchard trees. The fungus spreads through root grafts and nitidulid (Nitidulidae) vectors. Symptoms range from leaf wilting, foliar desiccation, and defoliation to limb dieback and mortality, varying by host species. This guide outlines diagnostic methods for wilt in oak and chestnut detailing protocols for B. fagacearum isolation and detection from infected host material and vectors. It includes molecular identification of axenic and mixed cultures using species-specific primers, as well as guidelines for the pathogen preservation and inoculations. While focusing on oaks and chestnut, these techniques can be adapted for diagnosing oak wilt in other susceptible hosts.