Biodiversity in and around Greenhouses: Benefits and Potential Risks for Pest Management

SIMPLE SUMMARY: The role of plant diversity near greenhouses is heavily debated because it may have both negative and positive effects on pest control inside greenhouses. In this review, we discuss these potential risks and benefits. Although there is the risk of an increased influx of some pests and of viruses transmitted by pests, we argue that biodiversity in the adjacent environment usually has limited effects on pest abundance in greenhouses in temperate climates, as most greenhouse pests in temperate climates are of exotic origin. The main benefit of increased biodiversity near greenhouses is the immigration of natural enemies that can suppress pests inside greenhouses. An open question is how this can be promoted by specific plant communities, plant characteristics, and habitats while minimising risks. Plant biodiversity inside greenhouses can also support biological control. We summarise general methods that growers can use to enhance pest control with functional biodiversity and suggest that it is particularly important to study how biodiversity inside and outside greenhouses can be linked to enhancement of biological pest control with both released and naturally occurring species of natural enemies. ABSTRACT: One of the ecosystem services of biodiversity is the contribution to pest control through conservation and stimulation of natural enemies. However, whether plant diversity around greenhouses is beneficial or a potential risk is heavily debated. In this review, we argue that most greenhouse pests in temperate climates are of exotic origin and infest greenhouses mainly through transportation of plant material. For indigenous pests, we discuss the potential ways in which plant diversity around greenhouses can facilitate or prevent pest migrations into greenhouses. As shown in several studies, an important benefit of increased plant diversity around greenhouses is the stimulation of indigenous natural enemies that migrate to greenhouses, where they suppress both indigenous and exotic pests. How this influx can be supported by specific plant communities, plant characteristics, and habitats while minimising risks of increasing greenhouse pest densities, virus transmission, or hyperparasitism needs further studies. It also requires a better understanding of the underlying processes that link biodiversity with pest management. Inside greenhouses, plant biodiversity can also support biological control. We summarise general methods that growers can use to enhance pest control with functional biodiversity and suggest that it is particularly important to study how biodiversity inside and outside greenhouses can be linked to enhancement of biological pest control with both released and naturally occurring species of natural enemies.