Natural pest regulation along a tropical agricultural landscape gradient: complexity counts

Agricultural intensification is a threat to arthropod natural enemies of crop pests in agricultural landscapes due to multiple reasons. This may disrupt the biological pest regulation in the agro-ecosystems and thereby affect their sustainability. Natural enemies are reliant on natural and semi natural vegetation in the landscape which serves as alternative resources and provide refuge, decline of which may affect pest regulation through both direct and indirect mechanisms. We examined how landscape complexity affects natural arthropod enemies, pest, intraguild predators (Insectivorous birds), predation rate and pest damage at different spatial scales. We modeled the interrelationship between different farm scale parameters through Structural equational models (SEM) at 1000m and 2000m. There was significant positive association between landscape complexity and coccinellidae and parasitic hymenoptera abundance. Arthropod predation rate on artificial plascticine caterpillar also increased significantly with landscape complexity at different spatial scale. Structural equational models revealed latent relationships between different farm level components which were not directly found through simple correlative models. Comprehensive studies incorporating direct and indirect effect of landscape complexity on farm level biodiversity elements is necessary for ecologically intensive farms in the future.