Pest survey card on Stegophora ulmea

This pest survey card was prepared in the context of the EFSA mandate on plant pest surveillance (M-2020-0114), at the request of the European Commission. Its purpose is to guide the Member States in preparing data and information for surveys for the causal agent of black spot disease of elm, Stegophora ulmea. These are required to design statistically sound and risk-based pest surveys, in line with current international standards. Stegophora ulmea is a well-defined and distinguishable fungal species of the family Sydowiellaceae. The fungus is a Union quarantine pest, currently not known to occur in the EU and present only in North America and Asia. Stegophora ulmea has two conidial stages: the first, during spring and early summer, produces infectious macroconidia dispersed by rain splash; the second, from mid-summer, produces non- infectious microconidia that act as spermatia. The pathogen mainly overwinters in perithecia in leaf debris from which airborne ascospores are released in spring. The fungus infects many elm (Ulmus) species and hybrids and also Zelkova serrata. Detection and delimiting surveys should target Ulmus species and hybrids and Z. serrata. The host species, being widely distributed in the EU territory (forests, cities, parks), and the EU climatic conditions are not considered to be limiting factors for the establishment of the pathogen, if introduced. Visual examination in spring for the symptoms on the leaves (yellow lesions and black spots), is the most effective method of detecting S. ulmea in the field. Identification of the pathogen is done in the lab by microscopic examination of acervuli from the leaves and/or morphological identification of the pathogen in pure culture. Molecular methods for detection and identification are not available.