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Effects of intercropping on the life cycle of the turnip root fly (Delia floralis)

behaviour, natural enemies and host plant quality

Björkman, Maria (2007). Effects of intercropping on the life cycle of the turnip root fly (Delia floralis). Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2007:125
ISBN 978-91-85913-24-4
[Doctoral thesis]

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The turnip root fly (Delia floralis) is a pest insect in the northern temperate regions of the world. If uncontrolled, it can cause severe problems in the production of brassica crops. This thesis examines how intercropping of cabbage (Brassica oleracea) and red clover (Trifolium pratense) affects the different life cycle stages of D. floralis. Such knowledge about the mechanisms involved is needed for developing intercropping systems with optimal pest reduction. A field trial was performed in Umeå, northern Sweden (63º45’N; 20º15’E), to study the effects of intercropping on D. floralis oviposition behaviour, and the impact of predators and parasitoids on D. floralis in the field. Intercropping was found to reduce D. floralis oviposition compared with monoculture. Furthermore, analysis of the spatial distribution of eggs within plots showed that the difference in egg numbers was greatest close to the border between the cultivation systems. This indicates that the effect of intercropping can be enhanced if D. floralis is provided with an alternative oviposition site. Natural enemies, in this case mainly predators, significantly reduced the final pupal numbers of D. floralis but this effect did not differ between the cultivation systems. However, the study showed that it is possible to retain the predation pressure in intercropped systems despite lower predator activity-densities and D. floralis egg numbers. A greenhouse experiment was performed to investigate effects of intercropping on development of D. floralis at different larval and intercropping densities and to analyse different aspects of host plant quality in the same system. It was found that D. floralis pupal weight decreased in response to both intercropping and larval density. This impaired larval development is likely to be explained by changes in host plant quality, which included decreased biomass, lower root nitrogen levels, higher root fibre content and altered glucosinolate concentrations. Information on plant responses to herbivory in competitive plant systems can be valuable in identifying quality aspects that are negative for insect development, which may further improve pest insect regulation in these systems.

Authors/Creators:Björkman, Maria
Title:Effects of intercropping on the life cycle of the turnip root fly (Delia floralis)
Subtitle:behaviour, natural enemies and host plant quality
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2007
Number of Pages:42
ALLI. Björkman, M., Hambäck, P.A. & Rämert, B. 2007. Neighbouring monocultures enhance the effect of intercropping on the turnip root fly (Delia floralis). Entomologia Experimentalis et Applicata 124, 319-326. II. Björkman, M., Hambäck, P.A., Hopkins, R.J. & Rämert, B. Evaluating the Enemies hypothesis in an intercropping system – effects of generalist and specialist natural enemies on the turnip root fly (Delia floralis). (Submitted) III. Björkman, M., Hopkins, R.J., Hambäck, P.A. & Rämert, B. Effects of intercropping and herbivore density on the development of the turnip root fly (Delia floralis) mediated by host plant quality. (Submitted). IV. Björkman, M., Hopkins, R.J. & Rämert, B. Combined effect of intercropping and turnip root fly (Delia floralis) larval feeding on the glucosinolate concentrations in cabbage roots and foliage. (Submitted).
Place of Publication:Uppsala
Associated Programs and Other Stakeholders:Z - SLU - Library > Odla mera
ISBN for printed version:978-91-85913-24-4
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:delia floralis, pest insects, life cycle, brassica oleracea, trifolium pratense, intercropping, insect control, natural enemies, animal developmental stages, oviposition, host plants, host pathogen relations, glucosinolates
Keywords:Oviposition, border effect, predation, parasitization, glucosinolates, NDF, lignin, induced response
Permanent URL:
ID Code:1656
Department:(NL, NJ) > Dept. of Crop Production Ecology
Deposited By: Maria Björkman
Deposited On:11 Dec 2007 00:00
Metadata Last Modified:22 Mar 2015 15:12

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