A new species of Contarinia Rondani (Diptera: Cecidomyiidae) that induces flower galls on canola (Brassicaceae) in the Canadian prairies

Abstract

A new species, Contarinia brassicola Sinclair (Diptera: Cecidomyiidae), which induces flower galls on canola (Brassica napus Linnaeus and Brassica rapa Linnaeus (Brassicaceae)), is described from Saskatchewan and Alberta, Canada. Larvae develop in the flowers of canola, which causes swelling and prevents opening, pod formation, and seed set. Mature larvae exit the galls, fall to the soil, and form cocoons. Depending on conditions, larvae will either pupate and eclose in the same calendar year or enter facultative diapause and emerge the following year. At least two generations of C. brassicola occur each year. Adults emerge from overwintering cocoons in the spring and lay eggs on developing canola flower buds. The galls produced by C. brassicola were previously attributed to the swede midge, Contarinia nasturtii (Kieffer) in Saskatchewan; here, we compare and list several characters to differentiate the two species.

Disjunction between canola distribution and the genetic structure of its recently described pest, the canola flower midge (Contarinia brassicola)

“…CFM is hypothesized to be native to Canada (Mori et al 2019), although knowledge of its biology is limited by the short history of its taxonomic existence. Prior to its description in 2019, the canola midge pests of the Prairie provinces were erroneously thought to be the swede midge, Contarinia nasturtii (Kieffer), a morphologically and ecologically similar congener of CFM.…”

“…Initial adult emergence occurs in June and July, during canola bud formation, with a second generation in August; however, CFM larvae have been observed in the field throughout the summer and into September, suggesting that they may produce more than two generations per year (Chen et al 2011;Andreassen et al . 2018;Mori et al 2019;Soroka et al . 2019).…”

“…Larvae are small, up to a few millimeters in length, and they feed within developing canola flower buds. This causes the buds to transform into galls, which then fail to flower or produce seed (Mori et al 2019). Due to their feeding behaviour and ability to produce multiple generations per year, CFM is potentially capable of causing significant impact on Canadian canola crop yields.…”

“…While several aspects of CFM ecology have been described (Mori et al 2019;Soroka et al . 2019), little is known about CFM population dynamics.…”

“…2019), little is known about CFM population dynamics. Prior genetic investigation of CFM was restricted to specimens sampled primarily from Saskatchewan and use of only a single mitochondrial gene (Mori et al 2019). There have been no assessments of CFM population structure at wider geographic scales, thus limiting effective monitoring and risk assessment across the canola producing region.…”