First observations of Mycosphaerella pini in Estonia

An aggressive disease of pines - red belt blight, caused by the fungus Mycosphaerella pini (anamorph Dothistroma septospora) was recorded for the first time in Estonia, in Järvselja Forest District, South Eastern Estonia.

Estonia is located in the centre of a geographic area subject to climatic change (Aasa et al., 2002). Forests have just experienced two series' of extreme weather events, accompanied by the simultaneous deterioration of the health of different tree species (Hanso & Drenkhan, 2007). Not only has there been declining health of the tree species growing in Estonia, close to the northern limit of their natural range or introduced from the south, but even the native, comparatively cold- and drought-resistant Scots pine (Pinus sylvestris) has suffered (Drenkhan & Hanso, 2006). It is therefore not surprising that new invasive diseases may occur on stressed pines, including red belt blight (Woods et al., 2005).

Examination of needle samples, collected in the autumn 2006 from a diseased Pinus nigra stand in Järvselja, resulted in the first observation of red belt blight in Estonia. Typical symptoms of M. pini infection (Anonymous, 2005) were observed, consisting of bright red belts, stripes and patches on pine needles, together with the conidia of the anamorph, D. septospora (21.6-35.8 x 1.8-2.8 µm, average 27.8 x 2.6 µm).

Before the autumn of 2007 several new records of the disease, always accompanied by the spores of D. septospora were made from native Scots pines in several young plantations in South Estonia. During the autumn of 2007, several ornamental Pinus mugo and P. sibirica trees were found that were badly infected by the disease, and one record was made from P. ponderosa. The teleomorph stage was not found during the first year of observations in Estonia.

Herbarium samples were deposited in the major herbarium of the country (Mycological Herbarium of the Estonian University of Life Sciences, TAA(M) 178675). The first Estonian isolation of M. pini was made from P. sylvestris onto the pine needle agar from the conidia of D. septospora on this host. The identity of the isolation was confirmed by partial sequencing of the Internal Transcribed Spacer (ITS) region at the Finnish Forest Research Institute and deposited in GenBank (EU330226, EU330227, EU330228). The analyses showed complete (100%) similarity with ca. 50 different sequences of Mycosphaerella pini in GenBank, originating from different countries (e.g. AY808291, isolated from Pinus nigra in Cracow, Poland; AY808294, isolated from P. sylvestris in Slovakia; and AY808295, isolated from P. mugo in Bavarian Alps, Germany).