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Research article - Peer-reviewed, 2007

Neighbouring monocultures enhance the effect of intercropping on the turnip root fly (Delia floralis)

Bjorkman M, Hamback PA, Ramert B


Knowledge of insect behaviour is essential for accurately interpreting studies of diversification and to develop diversified agroecosystems that have a reliable pest-suppressive effect. In this study, we investigated the egg-laying behaviour of the turnip root fly, Delia floralis (Fall.) (Diptera: Anthomyiidae), in an intercrop-monoculture system. We examined both the main effect of intercropping and the effect on oviposition in the border zone between a cabbage monoculture [Brassica oleracea L. var. capitata (Brassicaceae)] and a cabbage-red clover intercropping system [Trifolium pratense L. (Fabaceae)]. To investigate the border-effect, oviposition was measured along a transect from the border between the treatments to the centre of experimental plots. Intercropping reduced the total egg-laying of D. floralis with 42% in 2003 and 55% in 2004. In 2004, it was also found that the spatial distribution of eggs within the experimental plots was affected by distance from the adjoining treatment. The difference in egg-laying between monoculture and intercropping was most pronounced close to the border, where egg-laying was 68% lower on intercropped plants. This difference in egg numbers decreased gradually up to a distance of 3.5 m from the border, where intercropped plants had 43% fewer eggs than the corresponding monocultured plants. The reason behind this oviposition pattern is most likely that flies in intercropped plots have a higher probability of entering the monoculture if they are close to the border than if they are in the centre of a plot. When entering the monoculture, flies can pursue their egg-laying behaviour without being disrupted by the clover. As the final decision to land is visually stimulated, flies could also be attracted to fly from the intercropped plots into the monoculture, where host plants are more visually apparent. Visual cues could also hinder flies in a monoculture from entering an intercropped plot. Other possible patterns of insect attack due to differences in insect behaviour are discussed, as well as the practical application of the results of this study


border-effect; edge-effect; diversification; trap-crop; oviposition behaviour; companion plant; Delia radicum; cabbage root fly; Brassica pests; Diptera; Anthomyiidae

Published in

Entomologia Experimentalis et Applicata
2007, volume: 124, number: 3, pages: 319-326

Authors' information

Swedish University of Agricultural Sciences, Department of Plant Protection Biology
Björkman, Maria
Hambäck, Peter A

UKÄ Subject classification

Environmental Sciences related to Agriculture and Land-use
Agricultural Science

Publication Identifiers


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