First report of Chalara fraxinea affecting common ash in Hungary

In May 2008 dieback of common ash (Fraxinus excelsior) was observed in young forests in north-western Hungary next to Kapuvár. Symptoms included wilting of shoots, necrotic bark lesions with associated xylem discoloration and dieback of one-to-two year old twigs. Similar symptoms were also observed affecting up to 50% of some sapling regenerations and young forests near Sárvár (Fig. 1 and 2).

The pathogen was isolated on malt extract agar (MEA) from surface sterilized small pieces of the discoloured wood and incubated at 22.5°C in the dark. Colonies were slow growing, fulvous brown, and reached a diameter of 29-45 mm in three weeks (Fig. 3). Phialophore production was initiated a few days after four week old cultures were transferred to 6°C. Morphological features were typical for Chalara fraxinea (Kowalski, 2006; Halmschlager & Kirisits, 2008), namely olive-brown phialides (14-23 µm x 4-6 µm at the base and 2-3 µm at the collarette) and conidia 2.5-4 x 2-2.5 µm, (first formed conidia 6-7 x 2-2.5 µm) (Fig. 4). Pathogenicity was ascertained by wound inoculation of young tree shoots with pieces of fungal culture in situ. Sterile MEA was added to wounded control trees. Wilting of the leaves and discoloration of the wood were observed two weeks after inoculation. The pathogen was re-isolated from the discoloured wood tissue. No symptoms were observed in control trees.

This pathogen appears to be spreading throughout Europe after the first finding in Poland in 2006 (Kowalski, 2006). It was found in Sweden and Lithuania (J. Stenlid and R. Vasaitis, pers. comm. 2008), Germany (Schumacher et al. 2007), Austria (Halmschlager and Kirisits 2008). This is the first report of C. fraxinea in Hungary where the disease appeared in 2007.