Can flower strips increase beneficial arthropods in greenhouses?

Abstract

Apparent insect population declines represent potential ecosystem service losses, especially in terms of pollination and pest control. Such losses go hand in hand with the growth of intensive agricultural systems, landscape simplification, and disappearing “semi-natural” habitats. Agri-environmental schemes aim to contrast negative trends and enhance agricultural production by favoring conditions whereby benefits are derived from increased biological diversity. Flower strips, enriched meadows, and remnant or designed semi-natural areas serve as examples of Green Infrastructure elements commonly prescribed to connect farmland with the surrounding landscape in favor of beneficial arthropods. Ideally, pollinator, predator, and parasitoid functional groups use these spaces as foraging, nesting, and overwintering sites and in turn bring pollination and pest control services to adjacent cultivated areas. While various studies have explored how the different arthropod functional groups respond to different interventions, it is less clear if Green Infrastructure elements export beneficial arthropods to specific agricultural structures, especially greenhouses. We set out to measure the abundance of beneficial arthropods belonging to pollinator, predator, and parasitoid functional groups on two organic farms in the Veneto region of Italy. Arthropods were captured within commercial greenhouses using pan traps along transects at varying distance from greenhouse exteriors. Greenhouse areas had either 1) a flower strip installed nearby or 2) no flower strip installed nearby. Relative abundance of pollinators and “pest control” arthropods (parasitoids and predators, together) was modeled in relation to distance from greenhouse exteriors. Results indicate increased beneficial arthropod abundance in greenhouse areas with nearby flower strips, along with a negative correlation between abundance and distance from greenhouse exterior. This trend was more significant for pollinators than for pest control arthropods, and it did not necessarily hold for greenhouse areas lacking flower strips. As such, the flower strips considered in this study appear to accomplish, to a degree, their intended purpose of increasing beneficial arthropods in greenhouses. Future studies on flower strip composition and configuration in the context of greenhouses should focus on clarifying recommendations and quantifying net benefits in terms of ecosystem services leading to increased adoption of Green Infrastructure measures among farm managers.