A species-centered structural equation model reveals predator subsets driving biological control of Chilo sacchariphagus

Abstract: Pest species are embedded in complex multitrophic networks that shape their
dynamics. Systemic approaches integrating environmental covariates with multitrophic
interactions are therefore needed to link biodiversity to agroecosystem functioning and design agroecological cropping systems. However, these approaches face methodological challenges, particularly when the focal herbivore occupies a narrow trophic module and the ecological processes shaping interactions remain poorly understood. We applied a species-centered structural equation modeling approach to identify drivers of sugarcane borer Chilo
sacchariphagus infestation in sugarcane agroecosystems on Reunion Island. An intensive twoyear survey at 60 sampling points disentangled direct and indirect effects of environmental factors while highlighting the role of generalist predators within a broader multitrophic context. A filtering procedure identified key predator species before constructing a tailored structural equation model. Our results show that a refined predator aggregate comprising 11 morphospecies with diverse functional profiles exerted a strong negative effect on pest damage (β = –0.7). Additionally, the two dominant invasive ant species (Pheidole megacephala and Solenopsis geminata) exhibited a nonlinear, dome-shaped relationship with herbivory (β₁ = 0.5, β₂ = –0.6), suggesting a strong regulatory role. This study highlights the value of systemic approaches for understanding natural pest control. It underscores the importance of focusing on key predator groups while considering broader trophic interactions. Future research should clarify how predator functional traits complement each other and interact with the wider community to enhance pest regulation within the environmental context.