Vankosky: Development of a pheromone-based monitoring system for a newly identified Contarinia midge on the Canadian Prairies
Date: March 2020
Term: 3 years
Status: Completed
Researcher(s): Boyd Mori, University of Alberta and Agriculture and Agri-Food Canada; Meghan Vankosky, Agriculture and Agri-Food Canada; David Hall and Daniel Bray, University of Greenwich
SaskCanola Investment: $36,042
Total Project Cost: $58,133
Funding Partners: ACPC
Project Summary
The canola flower midge Contarinia brassicola Sinclair (Diptera: Cecidomyiidae) is a newly-described species that induces galls on canola, Brassica napus Linnaeus (Brassicaceae) (Mori et al. 2019). The galls prevent flowers from opening and subsequent pod formation. The small size of C. brassicola and its morphological similarity to sympatric species of midge makes detection and identification difficult, such that damage to crops by C. brassicola is often overlooked. Many cecidomyid midges of agricultural importance use sex pheromones (species-specific volatile chemical signals) to coordinate mate finding. Once properly identified, synthetic versions of these chemicals can be used as the basis of sensitive pheromone-based monitoring and management tools.
Here, we aimed to identify and synthesize the female-produced sex pheromone of C. brassicola and demonstrate its effectiveness in attracting males to traps in the field.
Using gas chromatography-electroantennography (GC-EAG) analysis of female-produced volatiles two chemical peaks were identified that elicited electrophysiological responses in male antennae. These peaks were initially characterized through gas chromatography-mass spectrometry (GC-MS) as 2,7-diacetoxynonane (major component) and 2-acetoxynonane (minor component), with the racemic compounds also eliciting EAG responses in male antennae. All four stereoisomers of 2,7-diacetoxynonane were synthesized and the naturally female-produced compound was shown to be primarily the R,S-isomer by analysis on an enantioselective GC column. The configuration of the minor component could not be determined because of the small amount present, but was assumed to be R. In field trapping trials conducted in Saskatchewan during 2018, the individual stereoisomers of 2,7-diacetoxynonane were unattractive to C. brassicola males. Re-examination of the analytical data suggested that a small amount of (R,R)-2,7-diacetoxynonane was also present in volatiles from female midges. During field trials in 2019, lures loaded with a 10 µg:1 µg blend of (R,S)- and (R,R)-2,7-diacetoxynonane caught large numbers of male C. brassicola and significantly more than other blends tested (Figure 1). Addition of 0.5 µg of (R)-2-acetoxynonane to this blend further increased the number of males caught.
Through this research, we identified the female-produced C. brassicola pheromone, and demonstrated that a lure containing 10:1:0.5 µg blend of (R,S)-2,7-diacetoxynonane, (R,R)-2,7-diacetoxynonane and (R)-2-acetoxynonane was highly attractive to males in the field. This identification will facilitate development of a pheromone-monitoring system for C. brassicola.
Figure: Mean (± SE) male C. brassicola (CFM) captured per week by traps baited with lures containing different amounts and isomers of the major (2,7,-diacetoxynonane) and minor ((2R)-acetoxynonane) pheromone components. Different letters above bars indicate significant differences (log-transformed data: GLMM χ2 = 305.1, d.f. = 6, p < 0.00001, followed by post-hoc test).
Acknowledgements: This research is part of the Canola Agronomic Research Program (CARP Grant 2017.13) with project funding provided by the Alberta Canola Producers Commission (Alberta Canola) and the Saskatchewan Canola Development Commission (SaskCanola). We acknowledge the assistance of A. Hamilton, J. Smith, J. Kim, and K. Saita in the completion of the fieldwork associated with this project.
References
Mori, B.A., L. Andreassen, J.D. Heal, J.R. Dupuis, J.J. Soroka, B.J. Sinclair. 2019. A new species of Contarinia Rondani (Diptera: Cecidomyiidae) that induces flower galls on canola (Brassicaceae) in the Canadian prairies. The Canadian Entomologist 151: 131-148.