Can mustard seed meal increase attacks by Aleochara spp. on Delia radicum in oilseed rape?

Abstract

Responses to mustard seed meal of two parasitic beetles, Aleochara bipustulata and A. bilineata, were assessed by measuring levels of parasitism of Delia radicum puparia and of root damage to oilseed rape, and by pitfall trapping of the beetles. Levels of parasitism and trap catches of A. bipustulata were higher in meal-treated plots than in untreated control plots; however, there were no significant effects on A. bilineata, numbers of D. radicum in roots or on levels of root damage. Olfactometry confirmed the absence of response by A. bilineata and showed that A. bipustulata is attracted to volatiles released by dry or wet mustard seed meal. From GC–MS, the most abundant volatiles from mustard seed meal were limonene and structurally-similar compounds. These results are discussed with respect to mechanism of attraction, the host finding cues used by the major parasitoids of D. radicum, and the value of mustard seed meal for enhancing biological control.

Keywords:

• Aleochara bipustulata
• Aleochara bilineata
• Delia radicum
• biological control
• oilseed rape

Acknowledgments

We are grateful to R. Fasnacht, Sugiez, Switzerland for providing field plots and technical support, and to S. Bacher, University of Bern, Switzerland for providing the olfactometer. H. D. Gesser, Department of Chemistry, University of Manitoba kindly supplied the monitor strip fabric, and W. Buchannon of the same Department operated the GC–MS. Funding was provided by the Canola Council of Canada, the Western Grains Research Fund, the Natural Sciences and Engineering Research Council of Canada and Agriculture and Agri-Food Canada.