Hymenoscyphus pseudoalbidus, the causal agent ofEuropean ash dieback

Abstract

Once the disease is established, management is hardly possible. The occurrence of a small fraction of partially tolerant trees constitutes hope for resistance breeding in the future. Healthy-looking trees should be preserved.

Fungi on stems and twigs in initial and advanced stages of dieback of European ash (Fraxinus excelsior) in Poland

“…Its successful expansion resulted mainly from anthropogenic factors and heterogeneous environmental conditions. It may also have benefited from some ecophysiological attributes that made it less susceptible than many other broadleaved tree species to attack over large areas by dangerous pests and pathogens (Wardle 1961;Marigo et al 2000;Amar et al 2010;Chen 2012;Pautasso et al 2013;Gross et al 2014). The situation has changed, however, in the last 20 years since the early 1990s large-scale dieback of F. excelsior has been found and observed increasingly in Poland and Lithuania (Kowalski 2001;Przybył 2002;Lygis et al 2005).…”

“…The situation has changed, however, in the last 20 years since the early 1990s large-scale dieback of F. excelsior has been found and observed increasingly in Poland and Lithuania (Kowalski 2001;Przybył 2002;Lygis et al 2005). Subsequently, F. excelsior dieback spread towards south, west and northern Europe and has reached epidemic level in most European countries, including Great Britain where it was first observed in 2012 (Husson et al 2011;Timmerman et al 2011;Pautasso et al 2013;Gross et al 2014).…”

“…Ash trees are infected by wind-dispersed ascospores of H. fraxineus produced in summer in apothecia on old leaf debris from the previous year and sporadically at the base of seedling stems Gross et al 2014;Kraj and Kowalski 2014). Disease symptoms include necrotic lesions on leaves, twigs and branches and sporadically on stem bases and roots, followed by wilting and premature shedding of leaves and dieback of tips, whole twigs and branches (Kowalski 2001;Chandelier et al 2010;Schumacher et al 2010;Gross et al 2014). The disease affects trees of all ages.…”

“…A new taxonomic designation was made by , who stated that under the rules for the naming of fungi with pleomorphic life cycles, adopted in July 2011 (Hawksworth 2014), the nomenclaturally correct name for the fungus causing the current ash dieback in Europe is Hymenoscyphus fraxineus with the basionym Chalara fraxinea, and Hymenoscyphus pseudoalbidus as a taxonomic synonym of H. fraxineus. Ash trees are infected by wind-dispersed ascospores of H. fraxineus produced in summer in apothecia on old leaf debris from the previous year and sporadically at the base of seedling stems Gross et al 2014;Kraj and Kowalski 2014). Disease symptoms include necrotic lesions on leaves, twigs and branches and sporadically on stem bases and roots, followed by wilting and premature shedding of leaves and dieback of tips, whole twigs and branches (Kowalski 2001;Chandelier et al 2010;Schumacher et al 2010;Gross et al 2014).…”

Effects of Host Variability on the Spread of Invasive Forest Diseases

“…However, where good records have been kept, mean spread rates have ranged between 30 and up to 75 km per year [103]. Regular monitoring of disease presence at the onset of its introduction to Norway initially gave an annual mean spread rate of 30 km, but then it increased rapidly in subsequent years averaging more than 50 km per year [104].…”