Conservation biocontrol: Principles and implementation in organic farming

Abstract

Conventional agricultural systems have become more intensive and pesticide-dependent over the last few decades. The contamination of the environment by pesticides, the use of mineral fertilisers, and habitat loss in many agroecosystems have led to a drastic decrease in plant and animal biodiversity. Ecosystem services provided by functional biodiversity (e.g., pollination, biological pest control) have also been negatively impacted. Conservation biocontrol aims to preserve and promote natural enemies to enhance pest control, avoid pest outbreaks and reduce pesticide reliance. However, despite a consensus on the main underlying principles, intentional practical applications are still rare. It is assumed that the diversity of habitats and resources in agroecosystems enhances the diversity and/or effectiveness of the natural enemies of pests. In this article, we argue that organic farming (OF) provides a promising framework for increasing conservation biocontrol at field and farm scales in agricultural landscapes. We looked at most of the commonly used OF practices at different spatio-temporal scales and discussed their effects on pest populations, natural enemy communities and biocontrol in agroecosystems. Several OF management practices such as crop diversification, use of organic fertilisers, diversification of resource plants at the field or landscape scales and land-use management are examined in our review. We particularly focused on possible strategies to enhance pest control measures in two case studies (i.e., orchard and annual crops) and discussed how and at which scales such strategies should be implemented. In the end, we identified knowledge gaps and bottlenecks that, if resolved, would help to enhance conservation biocontrol and applications in OF systems that aim to maximise both bottom-up (through plants) and top-down (through natural enemies) processes.