Inner bark of buckthorn showing healthy tissue (orange) and tissue diseased by fungi (brown/gray). Credit: Domini Brown
Background
Glossy and common buckthorn (Frangula alnus and Rhamnus cathartica, respectively) are exotic invasive shrubs that cause serious problems in Minnesota. Buckthorn aggressively spreads in forests and fields, displaces native vegetation, degrades habitat, and threatens normal ecosystem functioning. Buckthorn is also a host for other undesirable species that require management like soybean aphid and oat crown rust.
As a non-native species, buckthorn has lacked aggressive insect and disease pests in the US that can kill it. However, recent observations indicate that buckthorn is dying in some locations of Minnesota and Wisconsin. Preliminary studies have found many different fungi causing canker rot, wilt, and root rot in buckthorn, even preventing new growth from stumps. However, none have yet been evaluated as a potential biocontrol agent.
This research team will identify and study the effects of native fungi found on buckthorn for their potential use as a biological control against buckthorn.
Research questions
- What fungi are effective at colonizing and killing buckthorn?
- What fungi have the ability to prevent buckthorn stumps from resprouting?
- What effects do the identified fungi have on other non-target vegetation?
- What are the best application methods for using fungi as a biological control agent in the field?
Outcomes
Researchers have demonstrated that native fungi can be used successfully to control buckthorn. They can be used as mycoherbicides to kill stems or to colonize cut stumps and prevent resprouting. They did not find that light availability or stump diameter had any effect on mortality. ]
Specifically, the team found:
- Four species of fungi are pathogenic to buckthorn. Chondrostereum purpureum and Pezicula franguale subsp. frangulae caused the most severe symptoms.
- C. purpureum basidiospores, when inoculated into the ends of detached common buckthorn stems, cause extensive disease symptoms across all nutrient concentrations. These results suggest that nutrients in spore inoculum do not increase disease symptoms and thus can be excluded from future experimental formulations.
- Although C. purpureum basidiospores do not induce stump mortality as consistently or quickly as mycelial formulations, further research may show that a spore suspension could be an effective tool for buckthorn management that is more convenient to apply than using mycelium.
Publications
- Fungi Associated with Dying Buckthorn in North America (Forests, 2025)
Outreach
- Can Fungi Solve Our Buckthorn Problem?, The Toadstool Review, Minnesota Mycological Society, 2024
- US Forest Service Forest Health State Cooperators Meeting, 2024
- Minnesota Mycological Society Member Meeting, 2024
- Inver Hills Community College class lecture, 2024
- Annual Volunteer Appreciation Event, Friends of the Mississippi River, 2024
- Plant Pathology Department Seminar, 2024
- Upper Midwest Invasive Species Conference, 2024
- Plant Pathology Departmental Seminar, Cornell College, 2025
- Beyond Buckthorn: Innovative Strategies for Invasive Control and Habitat Restoration, webinar for the North American Invasive Species Management Association, 2025
- Minnesota Mycological Society meeting, 2025
- Saint Croix Watershed Research Rendezvous, Science Museum of Minnesota, 2025
- Minnesota Forest Health Workshop, 2026
- Wabasha Forestry Days, 2026
- Annual meeting of the Wisconsin Cooperative Invasive Species Management Areas, Wisconsin Department of Natural Resources, 2026
News and media
- Scientists think a fungus could conquer invasive buckthorn (The Minnesota Star Tribune, 2023)
- Beating the buckthorn blues (UMN News, 2024)
- Submit field observations of diseased or dying buckthorn (MITPPC, 2024)
- A Thorny Problem: Invasive buckthorn is damaging to landscapes and notoriously hard to control (Minnesota Conservation Volunteer magazine, 2024)
- Researchers make key breakthrough in fight against harmful plant wreaking havoc across US: 'Important first step' (The Cool Down, 2025)
- Fungi found on dying buckthorn could control the highly invasive species (UMN News, 2025)
- Buckthorn biocontrol with Ryan Franke (video by UMN Department of Plant Pathology, 2026)
- Fighting buckthorn with fungi (MITPPC, 2026)