Headwater stream environments and processes have been undervalued historically, despite serving as vulnerable keystone habitats and supporting downstream waterbodies through organic matter processing, carbon sequestration, and nutrient cycling. SPLAT® GM-Organic, a wax-based mating disruption treatment used to control the spread of Lymantria dispar dispar (European spongy moth), is applied aerially above headwater streams with an unknown impact on streams. The spongy moth is a destructive folivore, native to Eurasia, that was introduced to the eastern United States in 1869. The Slow the Spread Program (STS), funded by the US Forest Service, became operational in 2000 and has successfully limited the spread of the spongy moth, primarily via the use of mating disruption treatments. SPLAT® GM-Organic was introduced by ISCA Technologies in 2010 and became the sole mating disruption treatment used by the STS in 2017. Once applied aerially, SPLAT® sticks to various substrates, including leaves, and steadily releases the pheromone disparlure. By preventing spongy moth-induced defoliation of riparian vegetation, SPLAT® treatments are understood to have indirect positive effects on stream health; however, our research aims to identify the previously uncharacterized direct effects of the treatment on stream biological diversity and processes. The deposition of allochthonous organic matter (i.e. leaves) is a driving factor in headwater nutrient and carbon cycling. We hypothesize that deposition of the SPLAT® matrix into the stream mainly occurs through leaf fall, and the matrix, once present in the stream, may limit oxygen diffusion and serve as a food source for macroinvertebrates. We selected five headwater streams in the Slate River Watershed of Appomattox, Virginia, to be sampled from June 2024 to July 2026. Each stream was divided into an upstream control reach, a buffer, and a downstream experimental reach which was treated with SPLAT® GM-Organic on June 11, 2025 by the STS. Using a Before-After-Control-Impact (BACI) experimental design, the short- and long-term effects of SPLAT® treatments can be identified. We are sampling macroinvertebrates, algae, organic matter, water chemistry, dissolved oxygen, and SPLAT®. Our research will evaluate whether current treatment practices alter the ecological processes of streams.