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Various pathogens can cause diseases in forest trees. Many of them are microscopic and an infestation often only becomes visible through external disease symptoms. Tree diseases are typically only detected when they are already well established and widespread, and therefore it is difficult to eradicate them in the forest.
Fungi are the most important agents of forest diseases. However, bacteria, nematodes, oomycetes, phytoplasmas or viruses can also damage trees. Many pathogens are indigenous (e.g., some species of Armillaria), but international trade and global warming enable new pathogens to establish and spread in Switzerland (see also invasive species).
Particularly dangerous tree pathogens that are not yet present in Switzerland are classified as quarantine organisms. Special precautionary measures and a reporting obligation apply for these species. An example is Phytophthora ramorum (the causal agent of sudden oak death), which can infect various woody plants. Once introduced, dangerous pathogens can spread rapidly, as the fungal pathogen causing ash dieback has shown. Such organisms and possible control options, including biological control, can be studied under high-security conditions in WSL’s modern Plant Protection Laboratory.
WSL has two dedicated research groups for tree diseases: Swiss Forest Protection, the Swiss Centre of Expertise for forest protection issues, and the group Phytopathology. Within this framework, we operate a modern diagnostic laboratory and monitor the occurrence of dangerous forest diseases.