Abstract

Previous work has suggested that the condition of polyphagous predatory carabid beetles can be influenced by landscape structure and farming practice. However, earlier studies aimed at testing the effect of farming practice on insect condition and reproduction have not been designed to test this accurately because farms representing different cultivation systems have not had similar landscape complexity. In this study we measured the condition of the polyphagous predatory carabid beetles Harpalus rufipes, Pterostichus cupreus, P. melanarius, and P. niger from five pairs of conventional and organic farms in central east Sweden. The farms within each pair were near to each other and had similar size, land use, and landscape structure. The condition of the beetles was measured as the residuals from the regression between 1n(elytra length) and 1n(body mass). We show that the residuals for P. melanarius were positively correlated with their fat reserves. For P. melanarius, residuals were higher on farms where the fields had high perimeter-to-area ratio. The pooled residuals of H. rufipes, P. cupreus, and P. niger were positively correlated with the perimeter-to-area ratio and crop diversity. Pterostichus melanarius from organic farms had better condition than conspecifics at conventional farms, and for H. rufipes, P. cupreus, and P. niger combined there was a tendency toward better condition on organic farms than at conventional farms. Harpalus rufipes, P. cupreus, P. melanarius, and P. niger; which are all polyphagous predatory carabid beetles, are natural enemies of pest aphids in the agroecosystem. We conclude that, by manipulating landscape structure and composition, improvement in the condition of polyphagous predatory carabid beetles could be achieved, thereby potentially increasing populations of these beneficial insects.

Keywords

aphids; Carabidae; condition; beetle; farming practice; fat reserve; landscape composition; landscape structure; mass-length residuals; natural enemies

Published in

Ecological Applications
2001, Volume: 11, number: 2, pages: 480-488
Publisher: ECOLOGICAL SOC AMER

SLU Authors

• Östman, Örjan

  • Department of Ecology and Crop Production Sciences, Swedish University of Agricultural Sciences
    
  • Department of Entomology, Swedish University of Agricultural Sciences
    

• Ekbom, Barbara

  • Department of Entomology, Swedish University of Agricultural Sciences
    

• Bengtsson, Jan

  • Department of Ecology and Crop Production Sciences, Swedish University of Agricultural Sciences
    

• Weibull, Anki

  • Department of Ecology and Crop Production Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Ecology
Environmental Sciences related to Agriculture and Land-use


Publication identifier

DOI: https://doi.org/10.1890/1051-0761(2001)011[0480:LCAFPI]2.0.CO;2

Permanent link to this page (URI)

https://res.slu.se/id/publ/80314