Harnessing fungi’s ability to selectively kill buckthorn plants could provide the solution to control this invasive shrub, without relying on chemicals. First, though, researchers must assess the impact of many fungal species on buckthorn to seek candidates for the job. Blanchette Lab PhD student Ryan Franke has taken leadership in this research, analyzing over 400 fungal samples from dying buckthorn in Minnesota and Wisconsin to get a better picture of how and why different fungi are able to beat buckthorn.
Unwelcome guests
Like many non-native plants, common buckthorn (Rhamnus cathartica) was brought to North America by European immigrants in the late 1700s. Despite its popularity as a cold-hardy hedge in the US and Canada, its 200-year stay in North America has revealed its dangers to existing plant systems, such as crowding out native plants and negatively impacting ecosystems, and serving as an overwintering host for major crop pests such as soybean aphid and oat crown rust.
Remove the buckthorn? If only it were that simple—common buckthorn regenerates via stump sprouts and seedlings after initial removal, making it very labor intensive to get rid of manually.Other large-scale solutions like prescribed burns or herbicides can be harmful or deadly to other plants in the area. For this reason, a “mycoherbicide,” which uses a fungal pathogen as an active ingredient to target a specific host plant, is a more appealing solution.
Finding fungi
In 2023-2024, Franke and Blanchette teamed up with citizen scientists and MN and WI state agency personnel to collect a wide variety of already-dying buckthorn samples. The 86 buckthorn plant samples mostly consisted of common buckthorn, but also featured glossy and alder-leaved buckthorn. Symptomatic tissue, which most commonly consisted of cankers (localized or diffuse) but also included root rots, white rots, and fruiting bodies was taken from the buckthorn. Franke removed and isolated fungi from the samples, which were then cultured in the lab and used for DNA sequencing and identification.
Franke and colleagues found “46 putatively pathogenic species of fungi associated with declining common, glossy, and alder-leaved buckthorn,” including “many known canker, wilt, and root rot fungi.” See full publication for a complete description of methodology for isolation and identification, as well as listings of specific found species and their lifestyles. With this study completed and shared, researchers are now testing pathogenicity of specific fungi to determine the best candidates for a buckthorn-control mycoherbicide.
Franke, R.D.M.; Rajtar, N.N.; Blanchette, R.A. “Fungi Associated with Dying Buckthorn in North America.: Forests 2025, 16, 1148. https://doi.org/10.3390/f16071148