Previous studies have shown that this pathogen prefers temperatures around 20°C while its growth in pure cultures at 30°C proved to be very limited. The purpose of this study was to determine the effects of temperature on the development and growth of C. fraxinea in pure cultures and in plant tissues, as well as to test the heat tolerance of F. excelsior saplings. The sensitivity of fungus to heat in ash tissues was higher than in pure cultures. Low isolation success from diseased ash tissue after a five-hour hot water treatment at 36°C and the relatively high survival rate of ash saplings after hot water treatments at 36°C and 40°C indicate possibilities for the development of a C. fraxinea eradication method in ash saplings. Field monitoring showed that in hot weather periods, thermal conditions inside the ash tissues can be extreme enough to markedly decrease the viability of C. fraxinea in infected plant tissues.
Together with Italian forest pathologists we established the presence of the fungus Chalara fraxinea on common ash for the first time in Italy and proved its spread near Italo-Slovene border. The Koch's postulates were performed and the pathogenicity of the fungus was proven.
which is caused by the fungus Chalara fraxinea. We proved its presence by isolation to pure culture, by morphological characteristics in culture and by its microscopic characters. We conducted the test of its pathogenicity with Koch's postulates and proved its pathogenicity.
Ash dieback damage assessment was performed in nine ash seed collecting stands. Dead crown share and share of prematurely fallen leaves were assessed and other harmful organisms were determined. Average dead crown share at different locations was between 7 and 39 % and average share of premature fallen leaves was below 10 %. Weakened ash trees were often infected with Armillaria spp.
Massive ash dieback was first observed in the middle of 1990s in Lithuania and Poland. Disease spread quite fast and now different symptoms like wilting and premature shedding of leaves, necroses of leaf, leaf stalks and bark, top and shoot dieback and cankers of branches and stems, are reported from most of East, North and Central Europe. In autumn 2006 were first symptoms of disease discovered also in north-eastern part of Slovenia. In next years disease spread all over the country. Newly described fungus Chalara fraxinea was identified as causal agent of disease in 2006. Two years later telemorph of fungus was found. It was at first identified as long known saprophytic fungus Hymenoscyphus albidus, but recent molecular researches showed that teleomorph really belongs to new species H. pseudoalbidus. There are few different hypotheses about origin of fungus and appearance of disease that still need to be studied. Fungus was isolated from necrotic tissues of different ash species (Fraxinus spp.). Common ash (F. excelsior) and narrow-leaved ash (F. angustifolia) are the most susceptible species, while no symptoms have yet been observed on flowering ash (F. ornus). Endangered are trees of all ages, mortality is common amongst saplings and young trees. Disease is especially severe in humid places. European populations of susceptible ash species are seriously threatened. Anyway, because of resistance of individual trees hope for ashes still exists.