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Abstract Management of the Colorado potato beetle (Leptinotarsa decemlineata) is reliant on conventional insecticides that can negatively affect non-target arthropods. Calantha™ (active ingredient: ledprona) is a sprayable double-stranded RNA biopesticide specific forL decemlineataproteasome subunit beta 5 gene that triggers the RNA-interference pathway and is designed to have limited non-target effects. To test this hypothesis, we conducted two years of field trials in Idaho, Wisconsin, and Maine comparing arthropod responses to different insecticide regimes, with and without Calantha, targeting the Colorado potato beetle. Comparisons of arthropod abundance among treatments showed no evidence of effects of Calantha on non-target arthropods, including beneficials (predators, parasitoids), “neutrals” (i.e., non-pests), and other beetle species. Conventional insecticides generally showed more non-target effects, and responses were always stronger for arthropods from vacuum samples than pitfall samples. Insecticide programs featuring Calantha, especially in rotation with other biorational products, may reduce pests while preserving beneficial arthropods and contribute to biological control of arthropod pests in potato fields. 

Global apex scavenger declines strongly alter food web dynamics, but studies rarely test whether trophic downgrading impacts ecosystem functions. Here, we leverage a unique, disease‐induced gradient in Tasmanian devil (Sarcophilus harrisi) population densities to assess feedbacks between carcass persistence, subordinate scavenger guilds, and biogeochemical cycling. We further explored interkingdom and seasonal interactions by manipulating carcass access and replicating experiments in warmer, drier summer versus cooler, wetter winter periods. We show Tasmanian devil declines significantly extend carcass persistence and increase the flux of carcass‐derived nutrients belowground (e.g., by 18–134‐fold for ammonium). Greater nutrient availability reduces soil microbiome diversity by up to 26%, increasing the relative abundance of putative zoonotic pathogens. Nutrient subsidies also shift microbial communities toward faster‐growing taxa that invest less energy in resource acquisition, with implications for soil carbon sequestration. Rates of carcass decomposition were reduced in the winter, dampening soil biogeochemical responses and interkingdom competition. Notably, while less efficient scavenger guilds clearly facilitate carcass consumption, they were not able to fill the functional role of apex scavengers. Our study illustrates how trophic downgrading effects can ripple across all levels of ecological organization.