Current issue: 56(2)
Under compilation: 56(3)
Fomes annosus (Fr.) Cke. (now Heterobasidion annosum (s.str.)) has proved highly adaptable to varying conditions. Thus, the fungus is able to alter the pH as well as in alkalic as acid direction according to the original pH-grade. The fungus spreads mainly by basidiospores or by the sterile mycelium, but maybe also by the conidiospores. The fungus has spread through the temperate zone; in the tropical and sub-tropical zone it is found sporadically. There is a mention in the literature of at least 136 species in which it has been found. It is found in hardwoods but is most disastrous in conifers. The economic losses are considered biggest in England, Germany and Scandinavia.
The research has not been able to find a safe way to protect the trees growing on an infected site. The only way to limit the damage seems to be the use of mixed stands. Stump-protection has proved to be a relatively effective way to prevent the spread of the fungus to uninfected sites. The formerly used creosote has been mainly substituted by new chemicals, such as sodium nitrite. They act by altering the stump in a way that is favourable for antagonists to Fomes annosus, such as Trichoderma viride and Penicillium sp., or the recently presented Peniophora gigantea.
Although the fungus is found in many tree species, there is a difference in the relative resistance of different species. Among the conifers, the Abies-species (with exception of Abies grandis, A. alba and A. sachalienensis) are considered comparatively resistant. The species of Larix and Pseudotsuga are more resistant than those of Picea and Pinus.
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