Incidence and biology of Anisogramma virgultorum on birch in Scotland

摘要

Dieback of planted birch in Scotland has been causing concern since the late 1990s. The endemic fungus, Anisogramma virgultorum, Is pathogenic oil silver and downy birch and is a suspected causal agent of crown dieback at affected sites. In this study, A. virgultorum was found to be abundant and causing dieback of birch at nine planted stands surveyed across Scotland, but incidence and severity of this pathogen was much lower in site-natural birch stands. Experiments showed that ascospores of A. virgultorum were released in spring (April to June) from cankers on diseased birch branches to cause infection of newly flushing shoots.Canker development oil young shoots took approximately four to five months from initial infection in spring to the observation of black stromatal cankers containing living perithecia and fully differentiated ascospores by September. Birch shoots with A. virgultorum cankers tended to die back within one to two years after initial infection due to disruption of the hydraulic sufficiency of the affected shoot section. The taxonomic placement of A. virgultorum and its closest relative was also determined. The results of this study are discussed in the context of the importance of A. virgultorum to Scottish woodlands.