Bark beetles, their fungal associates and climate change: tackling multi-faceted risks with multidisciplinary research (Fung-i-nsect)

Coordinator: Eeva Terhonen, eeva.terhonen@luke.fi, LUKE



The unpredictable trajectory of forest-pest interactions can severely compromise the resilience of forests, especially under persistent abiotic stress conditions such as the recent drought events. Various bark beetle species have become more abundant and have been predicted to substantially expand their ranges due to climate change. The effect of this is, however, not limited to increased damage risk by the beetles alone, but also by their fungal associates. Bark beetles are known to transport various fungal species into their host trees, but a largely unanswered question is how climate change affects this relationship: can the range-expanding beetles also transfer new fungal species with them to areas where they have not been observed before, and if so, what does this mean to the local forest damage risk.

A possible example for such beetle-fungus interactions is the wide-spread death of mature Scots pine in Southern Finland during the hot and dry summer of 2021. This was largely due to the bark beetle Ips acuminatus that has become a more severe pest due to the more frequent hot and dry summers. Furthermore, Scots pine sapwood had turned blue due to virulent blue-stain fungal associates (Ophiostoma sp. and Ceratocystis sp.) of I. acuminatus. These fungi are necrotrophic pathogens that most likely help bark beetles overcome the host defence. However, the disease “Diplodia tip blight” caused by Diplodia sapinea was also discovered as being partly responsible for the death of these trees, and together with Heterobasidion annosum root rot they apparently caused unusually high mortality of mature Scots pines. Similarly, the hot summer of 2021 was beneficial for the European spruce bark beetle Ips typographus, causing higher bark beetle numbers and local damages in further north than has previously been recorded.

Similar phenomena have been observed in Denmark, Sweden, and Norway. The climate change has allowed the bark beetles (and their fungal associates) to overcome the resistance of their drought-stressed host trees, to have more generations during the year and finally, to expand their ranges into new areas. However, other stressors such as fungal pathogens (notably the carried blue-stain fungi, H. annosum s.l. and D. sapinea) are involved and as many of these fungal partners are benefitting from climate change, their interactions and effects should be studied together.


Overall long-term goal of the network

The network will bring together forest entomologists and pathologists around the topic of bark beetles and their fungal associates in a changing climate. Network will assess threats posed by changing climate, pests and pathogens. With researchers from Finland, Norway, Iceland, Denmark and Sweden, the consortium will address these questions across the entire Fennoscandian range. The network will also welcome scientists from outside the participating countries, e.g., from Baltic countries.

Long term goal is to support practical implementation of sustainable management of forest resources in the spirit of the concept Precision forestry when considering the new threats. Collaboration of scientists with different background on a scientifically challenging yet ecologically and economically important problem will provide an opportunity to pioneer research in the scientific forefront.

Additionally, this network aims to 1.) create a syllabus for a PhD course and share teaching materials (slides, videos), 2.) organize open access seminars and webinars for stakeholders, forestry practitioners and the general public to raise awareness of the lessons learned from participating countries.


Activities in 2023

We will organize three virtual meetings and one in-person meeting in Helsinki, Finland. We aim to include future young scientists to the network and syllabus for the content of the lecture series at universities will be planned. Similarly, a webinar will be held for forestry practitioners and stakeholders about the topic. One forum/discussion/synthesis -article over tripartite interactions of forest-bark beetle-fungi and the potential risks they pose for the Nordic countries under different scenarios of climate change will be drafted. Blog posts to the channels of the participating research institutes will be written and active social media (Twitter) posting about the project and its deliverables.


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