Phytopathogenic fungi can cause plant diseases that are difficult to control, including mass mortality of some tree species. The Fusarium oxysporum complex (sensu lato) is one of the most dangerous groups of phytopathogenic fungi, causing the death of conifer species, including Pinus sylvestris seedlings in forest and ornamental nurseries. Recently, non-chemical methods of plant protection have become the basis of integrated pest management (IPM) in the European Union (EC Directive). The possibility of protection of pine seedlings against the pathogen F. oxysporum using active substances from wood-destroying fungi commonly found in forests was examined. Methanolic extracts of Fomitopsis pinicola, Ganoderma applanatum, and Trametes versicolor were found to contain substances effective in both prevention and treatment of infected seedlings. G. applanatum and T. versicolor showed particular biological activity in increasing plant resistance. Efficacy, especially of the extract of F. pinicola, increased with concentration. Further field trials are needed to confirm the results obtained in laboratory tests on plant protection.

Fungi are important components of every ecosystem. In nature, they play a significant role as decomposers, decomposing organic matter into simple compounds available for plants. They are a curious group of organisms that attracts more and more interest not only among mycologists and phytopathologists, but also geneticists, biochemists and physiologists. Metabolic products of arboreal fungi show multidirectional action, including in the field of biological protection against harmful phytopathogens. Particularly invasive and difficult to control are soil fungi, phytobacteria and phytoviruses, which are widely spread in the rhizosphere. Moreover, the variety of pathogens is constantly increasing, and new forms are rapidly emerging, often more resistant to the biological control agents used so far.