Mycosphaerella dearnessii occurs in Slovenia

One-year-old needles of Scots pine (Pinus sylvestris) (Fig. 1A) and stone pine (P. mugo) (Fig. 1B) growing in parks in Bled and Ljubljana, Slovenia, were found dead or blighted in 2008 and 2009. A total of 15 trees had damage ranging from scattered twigs with affected needles to more extensive browning in the crown. All affected trees were removed and destroyed. When needles were placed in damp conditions, light yellow-brown to olive-green conidial slime was produced in short cirrhi from raised black areas with slits on both sides of the needles (Fig. 1C). The black areas (condiomata) contained light brown conidia, straight or curved, with a rounded apex and truncate base, thick and verrucose wall, and 0-6 septa. In water, they measured 30 (16-42) x 4 (2-5) μm (Fig. 2A, 2B). Mycelia arising from sterilised pieces of brown needles formed slow growing colonies on malt extract agar (MEA), quickly covered with a slimy mass of conidia. The characteristics of this fungus correspond to the Lecanosticta acicola anamorph of Mycosphaerella dearnessii, the cause of brown-spot needle blight (Anon., 2005). Samples of the diseased needles and pure cultures of the fungus were deposited in the Herbarium of the Slovenian Forestry Institute (Nos. 1666-1668).

We sprayed a spore suspension of the fungus in distilled water (67 x 10³ spores/ml) on needles of 12 shoots of three stone pines and enclosed the shoots in polyethylene bags for two days in June 2009. All treated plants were held in secure phytosanitary conditions. After two weeks, small yellow discolourations began to appear on the inoculated needles (Fig. 3A), turning brown after eleven weeks (Fig. 3B). We re-isolated L. acicola in October 2009 from the brown spots, on which stromata were now appearing (Fig. 3C). The needles of the control shoots sprayed with distilled water were undamaged. This is the first report of M. dearnessii in Slovenia. Brown spot needle blight was earlier reported throughout the Alpine region by Holdenrieder & Sieber (1995). More recently it has spread to the Czech Republic (Jankovsky et al., 2009).