Integrating reflective mulch with sufficient fertility sustains crop productivity while supporting sustainable pest management

Pest regulation and crop performance in agroecosystems emerge from interactions among agronomic management, plant physiological responses, and trophic dynamics, yet these drivers are often evaluated in isolation. In intensive vegetable systems, reliance on insecticide-based management can disrupt these ecological interactions without addressing the broader agroecosystem drivers of pest pressure. Western flower thrips exemplify this problem because their rapid population growth and feeding damage continue to challenge effective management. We conducted a two-year field study to evaluate how interacting agronomic and chemical factors shape pest suppression, predator responses, and crop yield. Using open-field peppers as a model system, a factorial experiment compared two insecticide programs (weekly spinetoram applications and untreated), three ground cover treatments (black mulch, diamond-reflective mulch, and bare soil), and three fertility rates (high NPK, sufficient NPK, and unfertilized). Mulch type and fertility consistently influenced plant performance. Thrips were lower under insecticide use and diamond-reflective mulch but increased under black mulch and fertilized treatments. Predator responses were taxon- and sampling-method dependent, reflecting insecticide use and bottom-up agronomic context, likely mediated by prey availability and habitat modifications. Diamond-reflective mulch paired with sufficient/high NPK produced comparable marketable yields, whereas additional insecticide inputs did not improve fruit quality once pest densities fell below economic thresholds. Collectively, these findings demonstrate that environmental modification can reduce pest pressure and improve crop productivity, while nutrient management shapes important tradeoffs between crop performance and herbivore pressure, suggesting that environmental modification may serve as a scalable lever for sustainable pest regulation within integrated pest management programs.