Indicator: Forest diseases
Diseases are caused by pathogens, primarily fungi in trees. All parts of a tree can become infected, leading to decreases in wood quality, productivity and occasionally death.
- Native pathogens co-exist with their hosts, achieving a balance over millennia, and are important for nutrient cycling, biodiversity and for other ecosystem processes.
- Disease effects from native pathogens typically occur over several growing seasons, causing gradual losses.
- Exotic introduced pathogens have caused extensive mortality to some tree species.
- Disease effects from exotic pathogens can occur quickly, resulting in rapid tree death.
Climate change and tree disease:
- Weather regulates host / pathogen interactions.
- Suitable environmental conditions when the host is susceptible can facilitate pathogen infection.
- Under climate change, we expect differences in pathogen behaviour, as weather patterns and environmental conditions change.
It is difficult to predict exactly how forest disease will be impacted by climate change. Monitoring and being prepared to respond are important for reducing losses.
Why is this indicator important?
- Economic losses can accrue when wood quality and volume are reduced within managed forests.
- Tree diseases can be managed to reduce economic losses by planting less susceptible tree species, using silvicultural treatments such as brushing or thinning and selecting genetically improved stock for planting.
What is the outlook?
- The effects of globalization, including increased trade, travel and tourism, can increase the risks of introducing exotic pathogens and their establishment, leading to increased damage to trees.
- We must remain vigilant to avoid the introduction of exotic pathogens, such as the oak wilt pathogen, Bretziella fagacearum, which is present in the northern United States.
- Technological improvements in DNA-based identification of forest pathogens are important tools in preventing the establishment of exotic pathogens.
What reporting frameworks does this indicator support?
- Montréal Process: 3.a
Sources and information
- Canadian Food Inspection Agency. Bretziella fagacearum (previously known as Ceratocystis fagacearum Oak Wilt) - Fact Sheet.
- Capron, A., Stewart, D., et al. 2020. In situ processing and efficient environmental detection (iSPEED) of tree pests and pathogens using pot-of-use-real-time PCR. PLoS ONE 15(4): e0226863.
- Ostry, M. and Laflamme, G. 2009. Fungi and diseases – natural components of healthy forests. Botany 98: 22–25.
- Pautasso, M., Schlegel, M., et al. 2015. Forest health in a changing world. Microbial Ecology 69: 826–842.
- Sakalidis, M., Feau, N., et al. 2016. Genetic patterns reveal historical and contemporary dispersal of a tree pathogen. Biological Invasions 18: 1781–1799.
- Sturrock, R., Frankel, S., et al. 2011. Climate change and forest diseases. Plant Pathology 60: 133–149.
- Cronartium harknessii photo by Tod Ramsfield.
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