Use of functional plants to enhance pest biological control in farming landscapes: progress and prospects

Functional plants are species or multi-species assemblages that are intentionally incorporated into agricultural landscapes to enhance pest control and contribute to overall agroecosystem health. Their deployment on-farm or in the wider landscape can enhance natural biological control of insect pests, weeds, and diseases, while also bolster pollination, soil health, and other ecosystem services. This is achieved through both direct and indirect interactions between the functional plants and the resident organisms within the agroecosystem. Interest in the use of functional plants for enhancing biological control has increased in recent years, as researchers and practitioners aim to leverage nature-based solutions to reduce dependence on synthetic pesticides. In this review, we propose the term ‘functional plants’ as a unifying concept to describe plants used in agroecosystems for specific ecological functions that contribute to pest management and other ecosystem services. We discuss the bottom-up and top-down mechanisms through which they affect biological control via natural enemies. We further explore the traits and other selection criteria that underpin the selection of functional plants, the magnitude of their impacts in terms of pest suppression, and practical considerations that relate to their adoption by end-users. In addition to highlighting their role in supporting pest biological control, we outline the most pressing knowledge gaps, research needs and implementation challenges.