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Invasive Pathogens
white spruce near Anchorage, AK..
Current Status
No serious exotic tree pathogens of native tree hosts have been confirmed in Alaska. Forest Health Protection is gathering information about a newly detected disease of spruce trees in Alaska, spruce bud blight. This disease is now known to be caused by three separate fungi that can be distinguished based on microscopic spore structures. The native/non-native status of Gemmamyces piceae) is unknown but it is well-distributed in Alaska and has been established for some time if it was introduced. Genetic work is underway with partners: visit the spruce bud blight page to learn more.
Background
Alaska is not safe from invasive pathogen introductions, particularly with increased trade and transportation and changing climate. Continued importation of live plant material and firewood are major potential pathways for invasive pathogen (and insect) introductions. Factors that may have protected Alaska from pathogen introductions in the past actually heighten our vulnerability. For example, low tree species diversity translates to potentially substantial, statewide impacts if introduced pathogens cause damage or mortality of our few dominant tree species; so far, the most devastating invasive forest diseases in North America have not affected our native trees. There can be lengthy delays between introduction and detection on our vast landscape, potentially allowing pathogens lag time to spread long distances via microscopic spores. Worldwide, there are no examples of the successful eradication of invasive plant pathogens established in forest ecosystems. Preventing invasive pathogens from entering Alaska must be the top priority.
Plant pathogens that are inconspicuous and minor in their native range can have major impacts in new habitats due to differences in host susceptibility and climate, which impedes our ability to anticipate new introductions. That said, Forest Health Protection and cooperators in Alaska have been working to identify potential invasive tree pathogens in Alaska, primarily based on host genus susceptibility (see Table). A thorough assessment of potential exotic tree pathogens requires a comprehensive list of native species for context. As tree pathogens are found and identified, they are compared to known native species to determine whether they are native or suspected of being introduced. Unfortunately, mycology and pathology in Alaska is not advanced to the point where such lists include all or most organisms. Field surveys and identification of tree pathogens should be a continuing, long-term goal of the forest health program. Importation of plants closely related to our native species is the most likely mode of invasive pathogen introduction.
Links to Resources and Publications
Ashiglar, S. M.; Hanna, J. W.; Ross-Davis, A. L.; Klopfenstein, N. B. 2014. The USDA Forest Service-RMRS forest fungi collection: Resource for fungal identification, developing biological controls, predicting invasive pathogens, and predicting potential impacts of climate change. In: Chadwick, K.; Palacios, P., comps. Proceedings of the 61st Annual Western International Forest Disease Work Conference; October 6-11, 2013; Waterton Lakes National Park; AB, Canada. Washington, DC: U.S.D.A Forest Service, Forest Health Protection. p. 127-130. Available here.
Černý, K., Pešková, V., Soukup, F., Havrdová, L., Strnadová, V., Zahradník, D., & Hrabetová, M. 2016. Gemmamyces bud blight of Picea pungens: A sudden disease outbreak in central Europe. Plant Pathology, 65(8): 1267-1278. Available here.
Jaklitsch, W. M. and H. Voglmayr. 2017. Three former taxa of Cucurbitaria and considerations on Petrakia in the Melanommataceae. Sydowia, 69: 81-95.
Klopfenstein, N. B.; Juzwik, J.; Ostry, M. E.; Kim, M.; Zambino, P. J.; Venette, R. C.; Richardson, B. A.; Lundquist, J. E.; Lodge, D. J.; Glaeser, J. A.; Frankel, S. J.; Otrosina, W. J.; Spaine, P.; Geils, B. W. 2010. Invasive forest pathogens: Summary of issues, critical needs, and future goals for Forest Service Research and Development. In: Dix, M. E.; Britton, K., editors. A dynamic invasive species research vision: Opportunities and priorities 2009-29. Gen. Tech. Rep. WO-79/83. Washington, DC: U.S. Department of Agriculture, Forest Service, Research and Development: 23-33. Available here.
Content prepared by Forest Pathologists Robin Mulvey and Loretta Winton, Forest Health Protection, robin.mulvey@usda.gov and loretta.winton@usda.gov
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