Pesticide-induced ecological traps and insect pollinator foraging network disruption in apple orchards compared to adjacent graveyard refugia

Abstract

Beyond acute toxicity, agricultural pesticide regimes fundamentally restructure insect foraging networks through complex, poorly understood community-level pathways. By comparing eight conventional apple orchards with adjacent pesticide-free graveyard refugia in Shopian, Kashmir, this study documents the ecological cascades triggered by intensive, calendar-based pesticide applications. Orchards supported 68% lower insect abundance and 55% lower species richness than paired graveyards, with hoverflies and solitary bees disproportionately suppressed. Plant-pollinator networks exhibited structural collapse: connectance declined by 46%, nestedness by 46%, and network-level specialization increased by 63% (all p < 0.01), reflecting resource-constrained rather than co-evolutionarily structured communities. Foraging niche breadth contracted significantly across all shared taxa (Paired t-test: t = 5.61, p < 0.001). A chi-square goodness-of-fit test formally demonstrated that April foraging visits were disproportionately concentrated on Brassica campestris relative to its floral availability (76.0% of visits versus 48.0% availability; χ² = 62.88, df = 3, p < 0.001), satisfying the primary analytical criterion for ecological trap identification: this species preferentially attracted over 70% of non- Malus foraging visits during peak neurotoxic insecticide application, in the complete absence of uncontaminated floral alternatives. A parallel trap effect persisted through May–June (χ² = 31.65, df = 3, p < 0.001), extending exposure risk across the season’s most biologically active phase. Functional homogenization followed, with long-tongued insects declining by 78% and functional richness by 62%, driven by direct toxicity and herbicide-mediated elimination of deep-corolla floral resources. These findings elucidate a mechanistic cascade from phenologically triggered trap formation through network collapse to functional homogenization. Conservation strategies must prioritize permanent pesticide-free refugia and temporally explicit restrictions on bee-toxic insecticide application throughout the April–June risk window.