First report of Neofusicoccum parvum causing canker and dieback on Alnus glutinosa in Portugal

In March 2022, sunken cankers were observed on the stem and branches of young and mature Alnus glutinosa trees in central Portugal (Canelas, 40°42’17’’N; 8°33’59’’W). Cankers were characterised by necrotic lesions on the outer and inner bark that progressively girdled the circumference of stem and branches causing extensive canopy dieback (Figure 1). The incidence of the disease was estimated at 70% (linear plot of 50 m long). To isolate the causal agent, 20 samples including twigs, branches and stems were collected from seven diseased trees chosen at random along the transect. Isolations were performed from ten chips (5 mm2) of inner bark and xylem tissues cut aseptically from the margin of the necrotic lesions and transferred onto Petri dishes containing potato dextrose agar (PDA).