Abstract
ContextWoody semi-natural habitats serve as permanent habitats and hibernation sites for natural enemies and, through spillover processes, they play an important role in the biological control of insect pests. However, this service is also dependent on the amount and configuration of the dominating woody habitat types: linear landscape elements (hedgerows, shelterbelts), and more evenly extended plantations. Relating natural enemy action to the landscape context can help to identify the effect of woody habitats on biological control effectiveness.ObjectivesIn the Central European agricultural landscapes such as in the Hungarian lowlands, where our study took place, woody linear elements are characterised by high, while woody areal elements, mostly plantations, by low biological and structural diversity. In this study, we aimed to determine which composition and configuration of woody linear and areal habitats in the landscape may enhance the effect of natural enemy action on plant damage caused by the cereal leaf beetle (CLB, Oulema melanopus).MethodsHerbivory suppression by natural enemies was assessed from the leaf damage difference between caged and open treatments. These exclusion experiments were carried out in 34 wheat fields on plants with controlled CLB infections. The results were related to landscape structure, quantified by different landscape metrics of both woody linear and areal habitats inside buffers between 150 and 500 m radii, surrounding the wheat fields.ResultsThe exclusion of natural enemies increased the leaf surface loss caused by CLBs in all fields. Shelterbelts and hedgerows in 150–200 m vicinity of the wheat fields had a strong suppressing effect on CLB damage, while the presence of plantations at 250 m and further rather impeded natural enemy action.ConclusionsOur results indicate that shelterbelts and hedgerows may provide a strong spillover of natural enemies, thus contribute to an enhanced biological control of CLBs.
Highlights
The importance of semi-natural habitats (SNHs) for natural enemies of crop pests has already been demonstrated in a number of studies (Geiger et al 2008; Woltz et al 2012; Alignier et al 2014; Sarthou et al 2014)
We aimed to determine which composition and configuration of woody linear and areal habitats in the landscape may enhance the effect of natural enemy action on plant damage caused by the cereal leaf beetle (CLB, Oulema melanopus)
The exclusion of natural enemies increased the leaf surface loss caused by CLBs in all fields
Summary
The importance of semi-natural habitats (SNHs) for natural enemies of crop pests has already been demonstrated in a number of studies (Geiger et al 2008; Woltz et al 2012; Alignier et al 2014; Sarthou et al 2014). Shelterbelts and hedgerows have been shown to enhance the abundance and diversity of natural enemies in the adjacent crop fields, supporting the biological control of different agricultural pests (see for instance: Holland and Luff 2000; Kujawa et al 2006; Thomson and Hoffmann 2009, 2010, 2013; Morandin et al 2011; Morandin et al 2014). This has been demonstrated to be based on metapopulation processes which affect the distribution of natural enemies in seminatural and crop habitat patches at the landscape scale (Samu et al 2018). An important mechanism that controls this process is the spillover of natural enemies across the non-crop—crop interface, which depends on the habitat identity of the patches, as well as on the structural features of the landscape (Tscharntke et al 2007)
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