Improving Heterobasidion annosum s.s. diagnostics to hinder disease spread in northern Finland

Heterobasidion parviporum and H. annosum s.s. are the most significant fungal pests in our forests. They cause losses of over 50 million euros annually. Studies have shown that Heterobasidion spp. benefit from global warming. This will likely lead to the spread of root rot in the north. Heterobasidion parviporum occurs throughout the country, but H. annosum s.s. has only been found sporadically in the north. The northernmost occurrence of the disease was recently found in Ylikiiminki. The symptoms caused by H. annosum s.s. in particular are difficult to identify on standing trees. More information is needed on the occurrence and spread of forest diseases, especially in Lapland and Northern Ostrobothnia. However, monitoring the diseases requires sufficiently good diagnostics of pathogens and their symptoms in northern areas. Control of root rot is most effective in areas where the disease is still rare. The northern specific features of the disease caused by H. annosum s.s. have not been described at all, and no geographical comparison of symptoms has been made.

The project's work packages will acquire damage identification material, which includes the selection of sample areas, description of disease symptoms and identification of damage. The species identification of the identification material required for the symptoms caused by H. annosum s.s. and fungi causing a similar syndrome on pine trees will be carried out in the laboratory. A diagnostic tool will be created from the description of the symptoms to identify the damage. Descriptions of the macroscopic symptoms of different fungi in diseased pine trees will be used to create determination formulas. The sites will be selected from Southern Lapland and the northern parts of Northern Ostrobothnia in cooperation with forestry professionals. The diagnostic tool will also include descriptions of the symptom and spore stages of different fungi with explanatory texts. In addition, the ability of fungi other than H. annosum s.s. isolated from the damage material to cause disease symptoms on pine trees will be verified. The isolated fungi will be inoculated into pine seedlings and the ability of the fungi to cause disease will be assessed from the seedlings. In addition, information is provided on the pest diagnostics of H. annosum s.s. and its mimic fungi, using forestry professionals and forest organizations as an aid. Disease caused by H. annosum s.s. and similar symptoms are caused by the pest fungi known to the public, and forest owners are instructed to monitor and take care of the health of their forests at free public events.