Mycosphaerella dearnessii M. E. Barr (Brown-Spot Needle Blight of Pine) in Austria

Nairobi

2012

S.282

Artikel aus einer ZeitschriftUnselbständiges Werk

200176442

Mycosphaerella dearnessii M. E. Barr (syn. Scirrhia acicola; anamorph: Lecanosticta acicola Thüm, syn. Septoria acicola) is an ascomycetous pine needle pathogen and the causal agent of brown spot needle blight. Potential hosts comprise various pine species and even Picea glauca can be infected when exposed to heavy spore loads. The disease is known from North, Central and South America, Asia, South Africa and Europe. Since it is widespread in North and Central America, it is assumed to be of Central American origin. The global spread of the fungus is attributed to the expanded pine trade in the last decades. In Europe M. dearnessii is mostly limited to local sites and often occurs on Mountain pine (Pinus mugo) and Scots pine (Pinus sylvestris) in urban habitats (parks, gardens) as well as in arboreta. In forests, M. dearnessii is known to occur on Pinus uncinata in swamps and more rarely in Pinus sylvestris / Pinus radiata stands. In Austria, brown spot needle blight was identified originally from Mountain pine (Pinus mugo) in 1996 in the town Hollenstein/Ybbs (Lower Austria). Annual surveys by the Federal Research and Training Centre for Forests, Natural Hazards and Landscape (BFW) from 1996 to 2007 revealed a slowly increasing number of infested trees (P. mugo, P. uncinata and P. sylvestris) but infestation was still limited to urban sites in that town. In August, 2008, however, the species was found for the first time in mixed forest stands on Scots pines (P. sylvestris) adjacent to the town of Hollenstein. In autumn 2009 newly infested trees were found at the border of the municipal area of Hollenstein close to further mixed pine forest stands. In autumn 2010 M. dearnessii was detected for the first time on urban trees in five other towns up to 40 km distant to Hollenstein. Austrian black pine (Pinus nigra austriaca) which is common in the town of Hollenstein and known to be susceptible was never infected by M. dearnessii. This point might be due to a probable competition effect between Dothistroma septosporum (Dorog.) M. Morelet, which is extremely common on this pine species in Austria, and M. dearnessii. Swiss stone pine (Pinus cembra) which was planted as an ornamental tree in Hollenstein was also never infected. Whether the disease spread naturally from Hollenstein to the other towns, or infections were the result of multiple introductions via infested plant material is subject of discussion. Pathogen spread can occur over short distances by rain splash and wind, however, it is also likely that spores can be transported by clothes, shoes, or vehicles. Heavily infested trees, suffering from intense needle losses for many years, show branch dieback extending upwards in the crown. It is very likely, that such trees become attacked by secondary invaders. Currently, a doctoral thesis is conducted at the University of Natural Resources and Life Sciences (BOKU), Vienna and the BFW. One goal of this thesis was to investigate population diversity and potential patterns of spread of M. dearnessii in Austria as well as genetic diversity of M. dearnessii in Europe and other continents.
Brown spot needle blight, Austria, spread of disease, host range, Mycosphaerella dearnessii, Lecanosticta acicola, Dothistroma septosporum.