Native prairie response to aminocyclopyrachlor (AMCP) was evaluated in the Northern Great Plains. AMCP altered plant communities and reduced foliar cover of introduced, high seral, and low seral forb species. After treatment, high and low seral monocots increased at both sites due to reduced competition from susceptible forbs. AMCP reduced richness, evenness, and diversity. Aphthona spp. were released in the Little Missouri National Grasslands in North Dakota in 1999 for leafy spurge biological control. Soil seedbank composition was sampled from two ecological sites to evaluate changes in the plant community. By 2014, leafy spurge abundance decreased 92% on average. Subsequently, Kentucky bluegrass increased, but has also been deterred by a slow reintroduction of native species. High seral forb species richness has doubled in both ecological sites since 1999. Aphthona spp. successfully controlled leafy spurge for over 15 yr without any additional control methods or costs to land managers.