The effects of the fungal pathogen Swiss needle cast (SNC) on its host species, Douglas-fir, and its timber harvest repercussions have been researched. However, more research is needed regarding the effects of SNC on understory species and, consequently, browsing ungulate species. This study analyzes the effects of various thinning methods on SNC and SNC’s influence on understory species richness, diversity, and cover. The goal is to articulate a clear dynamic of SNC in Sitka spruce and Douglas-fir - western hemlock zones to provide insights for guiding forest management. I will analyze the Olympic Natural Resource Center’s pre and post-treatment data from Siuslaw National Forest with statistical analyses to articulate patterns in SNC presence, thinning, and understory change. The early, mid, and late seral/thinned treatments vary in density and by species replanted. I expect that thinning will decrease SNC abundance and increase understory species richness. Additionally, I predict that the stands replanted with red alder and conifers will see a higher abundance of understory due to red alder’s nitrogen-fixing ability. The enhanced understanding of SNC and thinning’s interplay aims to educate current and future forest managers about ecologically responsible management.