Karmactive Staff
University of Minnesota researchers have identified 120 different fungi species growing on dying buckthorn trees, with 46 showing promise as potential natural controls for this highly invasive plant that plagues Midwest and Northeast forests.
The research team collected fungi samples from dying buckthorn at 19 different sites across Minnesota and Wisconsin, screening specifically for fungi that might be developed into a “mycoherbicide” – a fungal-based control method that could offer an alternative to chemical treatments.
“Our survey of dying buckthorn reveals a considerable diversity of naturally occurring fungi associated with buckthorn decline,” said Ryan Franke, lead author and graduate student in the University’s College of Food, Agricultural and Natural Resource Sciences. “This research is the important first step in developing a fungal-based control for invasive common buckthorn.”
Common buckthorn (Rhamnus cathartica) and glossy buckthorn (Frangula alnus) have become major problems since arriving in Minnesota from Europe in the 1850s. Originally planted as ornamental hedges, they now form dense thickets that crowd out native plants and degrade forest ecosystems.
What makes buckthorn particularly difficult to manage is its aggressive growth and remarkable resilience. When cut down, the stumps vigorously resprout. Its seeds remain viable in soil for a few years, constantly producing new saplings. The invasive shrub also serves as an overwintering host for crop pests like soybean aphids, creating problems for farmers.
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Current control methods have significant drawbacks. Chemical herbicides work but aren’t appropriate for ecologically sensitive areas where the risk of contamination is high. Mechanical removal is effective but extremely labor-intensive and often impractical for large areas.
This is where fungi might help. The researchers are now testing which of the 46 identified fungal species are most effective at causing disease in healthy buckthorn plants. Studies are underway to determine how well these fungi work when inoculated into healthy buckthorn, with the most promising candidates moving forward to larger field trials.
Some of the fungi being studied belong to genera known to cause cankers and root rot in woody plants, including species in Cytospora, Diaporthe, Diplodia, and Fusarium.
The concept of using fungi to control invasive plants isn’t entirely new. A related research project at Michigan Technological University is exploring Chondrostereum purpureum (silverleaf disease) as a potential buckthorn control. This fungus has already been licensed as an active ingredient in commercial mycoherbicide products in Canada, where it’s used to prevent hardwood stumps from resprouting.
The Minnesota research is funded by the University’s Minnesota Invasive Terrestrial Plants and Pests Center through the Minnesota Environment and Natural Resources Trust Fund, as recommended by the Legislative-Citizen Commission on Minnesota Resources.
Buckthorn control is a high priority for both private landowners and public land managers. In a 2018 survey, common buckthorn was the most frequently reported invasive plant across both forest and agricultural settings in Minnesota. A more recent workshop found that professionals would allocate 40% of a hypothetical invasive species management budget specifically for buckthorn control.
While the research is promising, it will take time to develop a usable mycoherbicide product. The team must complete thorough testing to identify which fungi are most effective against buckthorn while being safe for other plants. Future field studies will determine whether these fungi can be strategically deployed as practical tools for land managers battling this persistent invader.
