First report and pest risk analysis of the ambrosia beetle associated fungus Graphium euwallaceae in Germany

Abstract The fungus Graphium euwallaceae is associated with ambrosia beetles (Euwallacea sp.) and has been found in e.g. avocado trees, box elder, and evergreen maple. It is known to occur in California, Vietnam, and Australia. In early 2025, the fungal isolate AGQMy-2025-02 was obtained from a borehole on Barringtoniaacutangula (Lecythidaceae) in connection with an outbreak of the Euwallacea beetle in a tropical greenhouse in Germany and suspected to be G. euwallaceae. A combination of morphological and molecular methods employing barcoding across four gene regions (ITS, TEF1-α, SSU and LSU) and phylogenetic reconstruction based on ITS and TEF1-α was used to identify this isolate as G. euwallaceae. This is apparently the first detection of the fungus in Europe. There is no information, that G. euwallaceae is regulated as a quarantine pest in any plant health regulation, and it is so far neither listed in the annexes to Regulation (EU) 2019/2072 nor by the European and Mediterranean Plant Protection (EPPO). This paper describes the diagnosis and presents a pest risk analysis for this fungus.