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First report of eutypella canker of Acer pseudoplatanus in Europe

2006; Wiley; Volume: 55; Issue: 4 Linguagem: Inglês

10.1111/j.1365-3059.2006.01426.x

1365-3059

Dušan Jurc, ̧Nikica Ogris, Bernard Slippers, Jan Stenlid,

Yeasts and Rust Fungi Studies

In late May 2005, distinctive oval bark lesions were found on the trunks of Acer pseudoplatanus (sycamore) on Rožnik Hill in the centre of Ljubljana, Slovenia. A characteristic feature of the cankers was that the bark remained in place except at the centre (the oldest part). The cankers were located mostly on the lower portions of the trunks. Intensive surveys around the location revealed a further 19 affected trees by the end of June. The disease was well established and the main trunks of three trees had snapped and fallen over. The furthest distance between affected trees was 10·6 km, suggesting an initially slow spread. It is not known when the disease first appeared. White to light cream-coloured mycelial fans were present in the bark and were significantly more developed along the advancing edge of lesions. Perithecia were always present on the older parts of cankers and were extensive, with necks up to 5 mm long and poorly developed stroma. Ascospores measured 8·5 (5·5–12) × 3 (2–4) µm; asci 85·5 (61–117) × 7·5 (5–10) µm; and conidia 25 (12·5–35) × 2 (1–2·5) µm. This fungus was identified as Eutypella parasitica. Although the range of sizes was slightly different from those given by Davidson & Lorenz (1938), all other morphological characteristics agreed with the original description. The rDNA ITS regions of two isolates were sequenced (GenBank accession numbers DQ118964–5) and compared with the ex-type isolate of E. parasitica (CBS no. 210·39, GenBank accession number DQ118966). All three sequences were identical. In June 2005, trunks of sycamore were inoculated with two isolates of E. parasitica. After 40 days control wounds without the fungus had begun to heal, while inoculated wounds showed some advancing necrosis, but it was impossible to reisolate the fungus. Despite this, there is little doubt that the symptoms observed are due to E. parasitica, as disease development is slow, with up to 2 years required to obtain positive results (French, 1969). As a result, these trials will continue to be monitored. Eutypella canker of Acer spp. (maples) is a destructive disease, until recently found only in North America. Sycamore and other Acer spp. are widespread in Europe, and this first report from Slovenia is therefore of immediate concern.