Pesticides do not significantly reduce arthropod pest densities in the presence of natural enemies

• Published in: Ecology letters 2021-09, Vol.24 (9), p.2010-2024
• Main Authors: Janssen, Arne, Rijn, Paul C. J., Chase, Jonathan
• Format: Article
• Language: English
• Subjects: Arthropods; biological control; Chemical control; Chemical pest control; field experiments; Field tests; Growing season; Herbivores; insecticides; Mathematical models; Meta-analysis; Natural enemies; parasitoids; Pest control; pest resurgence; Pesticide application; Pesticides; Pests; population dynamics; Predator-prey simulation; predators; Prey; Side effects; Syntheses; Synthesis; transient dynamics
• ISSN: 1461-023X; 1461-0248
• DOI: 10.1111/ele.13819

Chemical pesticides remain the main agents for control of arthropod crop pests despite increased concern for their side effects. Although chemical pesticide applications generally result in short‐term decreases of pest densities, densities can subsequently resurge to higher levels than before. Thus, pesticide effects on pest densities beyond a single pest generation may vary, but they have not been reviewed in a systematic manner. Using mathematical predator–prey models, we show that pest resurgence is expected when effective natural enemies are present, even when they are less sensitive to pesticides than the pest. Model simulations over multiple pest generations predict that pest resurgence due to pesticide applications will increase average pest densities throughout a growing season when effective natural enemies are present. We tested this prediction with a meta‐analysis of published data of field experiments that compared effects of chemical control of arthropod plant pests in the presence and absence of natural enemies. This largely confirmed our prediction: overall, pesticide applications did not reduce pest densities significantly when natural enemies were present, which concerned the vast majority of cases. We also show that long‐term pesticide effectiveness is underreported and suggest that pest control by natural enemies deserves more attention. The effects of chemical pesticides on pest densities beyond a single pest generation may vary due to pest resurgence. Using simulations of mathematical predator–prey models, we show that when effective natural enemies are present, chemical pest control will not decrease pest levels throughout a growing season. This prediction was confirmed with a meta‐analysis of published data of field experiments comparing effects of chemical control of arthropod plant pests in the presence and absence of natural enemies.