A survey by the NDSU expansion trap found that a new insect called canola flower mosquito was discovered in canola fields in northern North Dakota in 2020, said Janet Knodel, an entomologist at the North Dakota State University expansion.
The rapeseed flower mosquito belongs to the family of the Cecidomyiidae (gall mosquitoes) in the order Diptera (flies).
The canola mosquito was recently identified and found to be widespread in Saskatchewan and Alberta, Canada.
“We received 10 pheromone baits from Canada to monitor for the first time in 2020 for canola mosquitoes, mainly along the northern North Dakota Plain,” Knodel said in a press release from Extension.
“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 Langdon Research Extension Center in Cavalier County had the highest number of rapeseed flies caught, and a total of 344 mosquitoes were caught in 2020, “Knodel said.
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,” Knodel said.
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 canola,” said 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 added. “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,” said 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.”