An experimental approach to testing the efficacy of management treatments for glossy buckthorn at Seney National Wildlife Refuge, upper Michigan

Glossy buckthorn (Frangula alnus) is an exotic invasive shrub within many Midwestern wetlands and adjacent ecotones, including those found in several National Wildlife Refuges. Where glossy buckthorn becomes established, it can form a dense homogenous monoculture, outcompete native shrubs, and alter other ecosystem processes. Active management of glossy buckthorn is critical to minimize the spread of this species, and to restore or rehabilitate those areas presently impacted. We tested the efficacy of herbiciding and scorching on glossy buckthorn survival. Treatments were implemented in concert with management efforts currently practiced at Seney National Wildlife Refuge in Upper Michigan. One year after applying 20% glyphosate to cut buckthorn stumps, we found no difference in resprout density between this concentration of herbicide applied by sponge to stumps, scorching stumps with a propane torch, or untreated controls (p > 0.05). Additional low-volume spraying of 5% glyphosate to resprouts the following year significantly (p < 0.001 ) reduced resprout density as compared to scorching and controls, with no difference between scorch treatments and the controls. Low-volume herbicide spraying reduced seedlings by 96% and 91% one and two years following treatment, with no difference in seedling density between scorching treatments and controls. The most effective management option for reducing glossy buckthorn appears to be repetitive herbicide application, possibly for more than two years.