The invasive ash dieback pathogen Hymenoscyphus pseudoalbidus exerts maximal infection pressure prior to the onset of host leaf senescence

Detection of Airborne Inoculum of Hymenoscyphus fraxineus and H. albidus during Seasonal Fluctuations Associated with Absence of Apothecia

“…Likewise, ascospores of H. albidus were detected (in low density) in one location in Belgium in early autumn [10]. Furthermore, in Norway, Hietala et al [13] registered the presence of H. albidus by quantitative PCR (qPCR) in a heavily infested stand with H. fraxineus at the end of July.…”

“…The characteristic black pseudosclerotial plate on the surface of the petioles serves the fungus to survive the winter [2]. The pathogen establishment on leaves is terminated before the onset of the leaf senescence [13]. Conidia, which are produced on the petiole in autumn at low temperatures [14], may act as spermatia for sexual reproduction, but most likely do not play any role infecting the host.…”

“…Both species may colonize living leaves of F. excelsior [15]. However, H. fraxineus fructifies earlier, which may enhance its colonization to the detriment of H. albidus [13]. The rapid invasion of H. fraxineus in Europe has been pointed out as the main cause of the vanishing of H. albidus in its natural habitat.…”

“…Several authors have examined the spore dispersal of H. fraxineus and H. albidus. Timmermann et al [12] and Hietala et al [13] employed seven-day automatic volumetric spore trap based on the description of Hirst [18] to investigate the diurnal and seasonal pattern of H. fraxineus in Southern Norway from the beginning of July until the end of September. Chandelier et al [10] applied rotating arm spore traps based on principles of Perkins [19] and McCartney et al [20].…”

Phenotypic variability of Fraxinus excelsior L. and Fraxinus angustifolia Vahl under the ash dieback disease in the Czech Republic

“…As independent variables, we considered mean annual air temperature and precipitation as well as temperature and precipitation from April till September corresponding with the vegetation period. With regard to the seasonal biology of H. fraxineus and its maximal infection pressure prior to the onset of host leaf senescence (Hietala et al 2013), we also considered the mean temperature and precipitation of summer months (June-September), warmest month (July mostly), and of September when the infection is manifested by the wilt and premature shedding of leafs. Along with annual means, only climatic variables with significant and nearly significant (P > 0.90) effects on biometric charac- Tables 3 and 4.…”