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ORIGINAL PAPER

Flower strips adjacent to greenhouses help reduce pest populations and insecticide applications inside organic commercial greenhouses Shu Li1 · Coline C. Jaworski2   · Séverin Hatt3 · Fan Zhang1 · Nicolas Desneux4 · Su Wang1 Received: 30 April 2020 / Revised: 14 September 2020 / Accepted: 21 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020

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. Keywords  Conservation biological control · Habitat enhancement · Companion plant · Insectary plant · Natural enemy · Pesticide · Predator · Trap crop

Key message Communicated by M. Traugott. Shu Li and Coline C. Jaworski equally contributed to this work. Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s1034​0-020-01285​-9) contains supplementary material, which is available to authorized users. * Su Wang [email protected] 1



Institute of Plant and Environment Protection, Beijing Academy of Agriculture and Forestry Science, Beijing 100097, China

2



Department of Zoology, University of Oxford, Oxford OX1 3PS, UK

3

Laboratory of Forest Ecology, Faculty of Agriculture, Kyoto University, Kyoto 606‑8502, Japan

4

UMR ISA, University Côte D’Azur, INRAE, CNRS, 06000 Nice, France



• Habitat enhancement for pest natural enem