Abstract

The effects of landscape complexity on natural pest control have been widely studied but remain difficult to predict, as they often interact with local management practices and other environmental factors. In this study, we tested whether and to what extent landscape complexity (compositional and configurational heterogeneity) interacts with local pesticide use intensity and the presence of a non-crop host plant (Pyracantha coccinea), to influence the incidence of Eriosoma lanigerum, its parasitism by Aphelinus mali, and the abundance of generalist predators. We surveyed 18 apple orchards across a landscape complexity gradient in central Chile, assessing their landscape characteristics within a 1-km buffer, pesticide use intensity, and the presence of P. coccinea hedgerows. Our results highlight the significant role of configurational heterogeneity, with smaller patch sizes favoring predator abundance, while larger, less fragmented patches were associated with increased aphid incidence and parasitism rates. Intensive insecticide use strongly suppressed aphid populations but also reduced parasitism by A. mali and the abundance of predators. The presence of P. coccinea hedgerows modulated these effects, partially compensating for the reduction of insecticides and serving as a population reservoir for A. mali, but its influence varied depending on the proportion of seminatural habitat in the landscape. These findings emphasize the importance of integrating landscape structure, local management, and key non-crop habitat features when designing biological control strategies.