Flower strips adjacent to greenhouses help reduce pest populations and insecticide applications inside organic commercial greenhouses

Shu Li,Nicolas Desneux,Su Wang,Fan Zhang,Séverin Hatt,Coline C Jaworski

doi:10.1007/s10340-020-01285-9

Abstract

Flower strips can play an important role in agro-ecosystems by supporting populations of pests’ natural enemies, thereby enhancing biological control. However, few studies have considered enhancing habitat for natural enemies around greenhouses. We conducted a two-year field experiment to (i) identify potential flowering species enhancing natural enemy populations but not pest populations; and (ii) evaluate how the presence of flower strips adjacent to greenhouses helped reduce pest abundance and insecticide use by attracting natural enemies inside greenhouses. We tested six flowering species in monofloral plots placed in flower strips adjacent to greenhouses and measured pest and predator abundance in monofloral plots but also on eggplants as well as eggplant yield and insecticide use inside greenhouses. All flowering species attracted more pests and predators than strips of naturally occurring weeds. Cosmos bipinnatus and Borago officinalis hosted high predator abundance and low pest abundance. Conversely, Tagetes erecta and Verbena x hybrida hosted intermediate predator abundance but high pest abundance, and Cirsium setosum and Centaurea cyanus hosted lower predator and pest abundances. Overall, both predator and pest numbers were higher at high flower density. Pest abundance was reduced by 43% in greenhouses adjacent to flower strips compared with control greenhouses, while predator numbers were 20 times higher, and insecticide use was reduced by 34%, but yields remained unchanged. Flower strips around greenhouses are therefore a promising, economically viable strategy to enhance pest control and to reduce insecticide use, and mixtures of flowering species in flower strips should be further tested to enhance the diversity of the predator community.

Highlights

Reducing pesticide use in agro-ecosystems is central to mitigate their negative impacts on invertebrate communities, including biodiversity loss, the disruption of ecosystem services and the overall destabilization of ecosystems (Desneux et al 2007; Geiger et al 2010; Lu et al 2012; Mohammed et al 2018; Pretty 2018)
We asked: (i) How do the flowering species differ in their potential to support populations of natural enemies, but not pest populations?; and (ii) How does the implementation of flower strips adjacent to greenhouses affect the abundance of pests and natural enemies inside greenhouses, and how does it affect the need for insecticide applications as well as crop yields? We investigated these questions in a 2-year experiment including six greenhouses of eggplant crops in an organic greenhouse commercial farm in northern China
We showed that the implementation of flower strips adjacent to greenhouses helped decrease pest pressure on vegetable crops inside greenhouses, with a significant increase in predator numbers inside greenhouses

Summary

Introduction

Reducing pesticide use in agro-ecosystems is central to mitigate their negative impacts on invertebrate communities, including biodiversity loss, the disruption of ecosystem services and the overall destabilization of ecosystems (Desneux et al 2007; Geiger et al 2010; Lu et al 2012; Mohammed et al 2018; Pretty 2018). Enhancing floral resources in agro-ecosystems via the establishment of flower strips within and around crop fields has been shown to promote populations of natural enemies and the regulation of pest populations in neighboring fields (Pfiffner et al 2009; Balzan et al 2016; Tschumi et al 2016a, b; Hatt et al 2019a; Snyder 2019) This is because flowers can provide resources to natural enemies, including complementary food resources such as pollen and nectar, resources for alternative hosts or prey, or shelter or reproductive sites (Baggen et al 1999; Bugg and Waddington 1994; Lu et al 2014). This in turn allowed a reduction in insecticide applications by 70% and resulted in an increase in rice yields by 5% and in economic benefits by 7.6%

Objectives

Methods

Results

Conclusion