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Doctoral thesis, 2016

Food webs in agroecosystems

Roubinet, Eve

Abstract

The management of insect pests in modern agriculture is dominated by chemical control, despite wide recognition of its detrimental impact on the environment and human health. As a sustainable alternative, the service of biological control of insect pests is provided by a diversity of natural enemies, such as ground dwelling carabids and spiders. A better understanding of natural enemy communities and the feeding relationship between natural enemies and their prey is therefore crucial to better conserve and promote the provisioning of biological control in agricultural fields. To this end, we quantitatively summarized published studies that addressed the relationship between increased natural enemy diversity and biological control and studied moderation by biotic and abiotic factors. The results of this meta-analysis support an overall positive effect of increased natural enemy diversity on herbivore suppression, and suggest this effect is lessened by an increase of prey diversity. I then focused on communities of generalist, ground dwelling predators controlling aphids in cereal fields. I used recently developed DNA based molecular gut content analysis to study the feeding relationships between predators and their prey, i.e., food webs, and their implications for biological control. I investigated the effects and underlying mechanisms of increased predator diversity on aphid biological control in manipulative field cage experiments, and identified feeding interactions in relation to the availability of predators and prey during the growing season in field conditions. I showed that generalist predators appear to be functionally redundant in the provisioning of cereal aphid biological control, when considering short time periods. However, when the entire cropping season is considered the importance of different predators as aphid biological control agents varied, which suggests that high predator diversity may provide a more stable biological control service over time. The findings of this thesis support the design of conservation strategies that promote predator diversity and high levels of non-pest extraguild prey in order to sustain generalist ground dwelling predators and secure their contribution to biological control services in agricultural fields.

Keywords

Natural enemies; Carabids; Spiders; Aphid; Cereal; Redundancy; Stability

Published in

Acta Universitatis Agriculturae Sueciae
2016, number: 2016:29
ISBN: 978-91-576-8560-5, eISBN: 978-91-576-8561-2
Publisher: Department of Ecology, Swedish University of Agricultural Sciences

Authors' information

Roubinet, Eve
Swedish University of Agricultural Sciences, Department of Ecology

UKÄ Subject classification

Environmental Sciences related to Agriculture and Land-use
Agricultural Science

URI (permanent link to this page)

https://res.slu.se/id/publ/76830