NDSU Extension survey detects potential canola insect pest in North Dakota

The rapeseed flower mosquito belongs to the family of the Cecidomyiidae (gall mosquitoes) in the order Diptera (flies).

The rapeseed flower mosquito was recently identified and found to be widespread in Saskatchewan and Alberta, Canada.

“We received 10 pheromone baits from Canada to check for rapeseed mosquitoes for the first time in 2020, mainly along the northern plain of North Dakota,” says Knodel.

“At the end of the trap, six of the ten trap sites in five counties were positive for rapeseed mosquitoes: Bottineau, Cavalier, Pembina, Towner and Walsh. The highest numbers of canola mosquitoes were caught at the Langdon Research Extension Center in Cavalier County. A total of 344 mosquitoes were caught in 2020, ”says Knodel.

The adult rapeseed flower mosquito is a small (less than 2 millimeters long), inconspicuous brown fly.

“Farmers and Boy Scouts are unlikely to notice them in the field because of their cryptic color and small size,” says Knodel.

The immature stage is a small, white, maggot-like larva. Larvae feed and injure the flower buds by causing swelling (or bile) that prevents the flowers from opening. Damaged flowers will not produce pods or seeds. Damaged flower buds are elongated and bottle-shaped and form a closed flower gall.

“Canadian entomologists are unaware of the economic impact of this new Contarinia mosquito in rapeseed,” says Knodel. “Little is known about pest control.

“Canadian entomologists observed that early-planted canola (mid-May) had more mosquito-damaged pods than late-planted canola (early June),” she adds. “Insecticide seed treatments have been tested to control the rapeseed mosquito, but no negative effects on mosquito damage to the pods have been found. This is not surprising as the adult mosquito emerges about four to six weeks after sowing, while activity to treat insecticidal seeds wears off about three to four weeks after sowing.

“Future trapping and field surveys will be critical to the early detection and population monitoring of canola mosquitos in canola grown in North Dakota,” says Knodel. “This will help the canola industry so we will know when these mosquitoes are high in population and a threat to canola production in North Dakota.”

The Northern Canola Growers Association and the US Department of Agriculture’s Plant Protection and Pest Control Implementation Program – Enlargement support the survey.