Pheromone trapping for midges (Diptera: Cecidomyiidae) in canola

Swede midge, Contarinia nasturtii (Kieffer) and canola flower midge, Contarinia brassicola Sinclair, were monitored using delta-style pheromone traps in the major canola, Brassica napus L., producing areas of North Dakota. Traps were monitored weekly for Contarinia midges from mid-June through mid-August (rosette through ripening crop stages). Swede midge is an invasive species, which can cause significant yield loss to Brassicaceae crops. Swede midge larvae cause feeding injury by deforming leaves, shoots and producing flower galls. All pheromone traps monitored for swede midge were negative for a total of 117 trap sites in 15 counties during 2015 and 2017-2020. Canola flower midge is a new species that was recently described infesting canola in 2019 in Saskatchewan and Alberta, Canada. Larvae injure the flower buds by causing a gall, and damaged flowers do not produce seeds or pods. Ten pheromone traps for canola flower midge were monitored for the first time in 2020 in seven counties along the northern border of North Dakota-Canada. Six of the 10 traps sites were positive for canola flower midge in five counties representing new county, state and U.S. records. In 2021, canola flower midge was found at five of the 10 trap sites in five counties. A total of 11 counties of North Dakota were monitored for canola flower midge in 2020 and 2021. Peak trap catches for adults occurred from late July through mid-August. Future trapping and field surveys will be essential for early detection of these Cecidomyiid midge species in North Dakota’s canola.