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• t APPENDIX C. Methods for Controlling Exotic, Invasive Plant Species Trees and Shrubs Common Buckthorn, Tartarian Honeysuckle,Siberian Elm,and Black Locust are some of the most common exotic woody species likely to invade native woodlands or prairies in Minnesota. Buckthorn and honeysuckle are European species that escaped and invaded woodlands in many parts of the country.They are exceedingly aggressive and,lacking natural diseases and predators, can out-compete native species. They remain photosynthetically active longer than most other native shrubs and trees,which gives them a competitive advantage. The seeds are disseminated by birds,which make them especially problematic in open woodlands, savannas,and overgrown prairies. They also benefit from the net actions of invasive earthworms, fire suppression,and high deer populations, forming a synergy that helps set the stage for their establishment and dominance. Invasions eventually result in dense,impenetrable brush thickets that greatly reduce ground-level light availability and can cause declines in native species abundance and diversity. Siberian elm,native to eastern Asia,grows vigorously, especially in disturbed and low-nutrient soils with low moisture. Seed germination is high and seedlings establish quickly in sparse vegetation. It can invade and dominate disturbed areas in just a few years. Black locust is native to the southeastern United States and the very southeastern corner of Minnesota. It has been planted outside its natural range (it was promoted as an erosion control species and a soil stabilizer partly because it was falsely assumed to be a nitrogen fixer,and since it quickly colonizes bare slopes), and readily invades disturbed areas. It reproduces vigorously by root suckering and can form monotypic stands. Biological Control Currently there are no biological control agents for non-native woody plants in Minnesota. Recently,an 11-year study conducted by the DNR and University of MN resulted in the conclusion that there were no viable biological control agents for common or glossy buckthorn,based in part on the lack of damage to the host plants and a lack of host specificity (http://www.dnr.state.mn.us/invasives/terrestrialplants/woody/buckthorn/bioco ntrol.html). Chemical Control The most efficient way to remove woody plants that are 1/2 inch or more in diameter is to cut the stems close to the ground and treat the cut stumps with herbicide immediately after they are cut,when the stumps are fresh and the chemicals are most readily absorbed. Failure to treat the stumps will result in resprouting, creating the need for future management interventions. Friends of the Mississippi River Bailey Point Nature Preserve NRMP 75