<p>Invasive plants often alter soil and microbiomes to their advantage. The enhanced mutualism hypothesis suggests that invaders promote beneficial biota, such as arbuscular mycorrhizal fungi (AMF), creating a positive feedback loop that enhances their growth. Leafy spurge (<i>Euphorbia virgata</i>), a major invader in the Northern Great Plains, is highly mycorrhiza-responsive. Suppressing AMF may reduce its invasiveness and improve native plant competitiveness, particularly grasses that are less reliant on mycorrhizae. To test this, we conducted a factorial field experiment across 25 blocks at nine sites, combining fungicide, herbicide, and mowing treatments. We assessed plant composition, biomass, and nutrient content; as well as soil microbiome composition using fatty acids. Fungicide application reduced leafy spurge biomass, phosphorus content, and AMF abundance in the soil, without affecting total fungal abundance or the fungi-bacteria ratio. This suggests AMF are key to leafy spurge success. Both fungicide and herbicide increased grass abundance, but with different effects: herbicide favored exotic grasses, while fungicide increased native grass species richness when combined with herbicide. Thus, fungicide offset herbicide-driven declines in species richness. Fungicide could thus be a valuable tool for managing AMF-dependent invaders like leafy spurge. When paired with herbicide, it may enhance native grass recovery compared to herbicide alone, although broadleaf plant species remain susceptible to non-target herbicide effects. If exotic grasses are abundant within the system, there remains significant risk for secondary invasion. Further research is also needed to assess potential non-target effects of the fungicide as the long-term consequences remain unclear.</p>