Distribution and life history of Contarinia brassicola (Diptera: Cecidomyiidae) in canola (Brassica napus) grown on the Canadian Prairies

Abstract

Contarinia brassicola Sinclair (Diptera: Cecidomyiidae) is a recently described species found infesting canola (Brassica napus L. and Brassica rapa L., Brassicaceae) in western Canada. There is concern that C. brassicola could have economic impacts on canola production. To learn about its biology, distribution, natural enemies, and potential impact, we conducted a prairie-wide survey in western Canada and field studies using emergence cages and plant dissections between 2017 and 2019. Results of a transect-based survey conducted in Alberta, Saskatchewan, and Manitoba indicated that C. brassicola is widely distributed in western Canada. Two species of parasitic wasp were reared from C. brassicola larvae collected during the survey. We found that C. brassicola can have multiple generations per year, with the first peak of adult emergence occurring in early July with the onset of the susceptible crop stage. Adult midge and larvae may be found from June until early autumn. Midge larvae appear capable of extended diapause over multiple years. During this study, we found that C. brassicola damage was restricted to developing flowers. In the vast majority of fields surveyed, C. brassicola occurred in low population densities and was unlikely to impact yield in those fields.

Components of the Female Sex Pheromone of the Newly-Described Canola Flower Midge, Contarinia brassicola

“…Results of phylogenetic analyses also supported C. brassicola as a distinct species within the genus Contarinia (Mori et al 2019). Contarinia brassicola appears to be the main species of Contarinia on canola across the Canadian prairies, where C. nasturtii has not been detected since 2007 (Mori et al 2019;Vankosky et al 2022). The origin of C. brassicola, and its importance as a pest species threatening the $30 billion Canadian canola industry (Canola Council of Canada 2021), remain to be determined.…”

“…Contarinia brassicola adults begin to emerge in June and July on the Canadian prairies, which coincides with bud formation This paper is dedicated to the memory of Professor Kenji Mori who taught us so much about the structure and stereochemistry of natural products and was a much-loved friend and colleague. and early flowering in canola (Mori et al 2019;Vankosky et al 2022). Females lay eggs on developing canola buds, and, after hatching, larvae feed cryptically within the flower bud resulting in gall formation.…”

“…Mature larvae leave the galled flowers and form cocoons in the soil. A portion of the larvae pupate and emerge as a second generation, while others appear to undergo diapause for emergence the following year (Campbell et al 2020;Vankosky et al 2022). To date, C. brassicola has only been found in North America (Campbell et al 2020;Mori et al 2019).…”