Semi‐natural habitats drive species‐specific pest responses in tropical eggplant farms: Direct and indirect pathways to biological control

The proportion of semi‐natural habitats is a major driver of arthropod natural enemy and pest populations in agricultural landscapes. However, the mechanisms through which semi‐natural habitats govern pests and their natural enemies remain poorly understood, especially in tropical smallholder farming systems. Semi‐natural habitats can affect pests directly (by providing alternative resources or creating dispersal barriers and reducing host plant availability) or indirectly (by enhancing natural enemy populations that provide top‐down control), yet few studies have simultaneously explored both pathways. In this study, conducted in 20 tropical smallholder ‘brinjal’ or ‘eggplant’ ( Solanum melongena L. (Solanales: Solanaceae)) farms in Eastern India, we used structural equation models to examine how semi‐natural habitats directly and indirectly influence arthropod natural enemies, pests, predation pressure and subsequent pest damage. Semi‐natural habitats had a strong positive effect on total natural enemy abundance and predation pressure. For pests, the effects of semi‐natural habitats were species‐specific, with semi‐natural habitats directly influencing leafhopper ( Amrasca biguttula (Ishida, 1913) (Hemiptera: Cicadellidae)) abundance, while there was no direct or indirect effect for whiteflies. For brinjal shoot and fruit borer ( Leucinodes orbonalis Guenée, 1854 (Lepidoptera: Crambidae)), no strong direct or indirect effects of semi‐natural habitats were detected, though borer abundance significantly predicted fruit damage. Our study highlights the complex, pest‐specific nature of landscape‐mediated biocontrol and underscores the importance of considering both the direct and indirect pathways for developing sustainable and ecologically intensive farming systems.