Affectionately known as a ‘ticking pest time bomb’, a wheat midge outbreak is on everyone’s radar this year. Despite the dry spring conditions, areas of Western Canada received significant rainfall in late May, triggering growers to be on the lookout for wheat midge pressure.
While the 2023 Alberta and Saskatchewan wheat midge forecast maps are primarily green, with a handful of yellow and red hot spots, they do predict increased numbers of wheat midge compared to the relatively low counts for the 2022 forecast (based on 2021 data). Dr. Tyler Wist, research scientist of field crop entomology with Agriculture and Agri-Food Canada in Saskatoon explains that, despite last year’s low pest pressure predictions, some areas saw wheat midge hot spots. And those populations where likely picked up in the fall 2022 soil samples that were used to create the 2023 wheat midge forecast maps.
“If we get rain in those predicted zones, and some regions already have, growers can expect midge damage this year,” says Dr. Wist. “The prediction maps are a tool, but the real indication of wheat midge is rainfall in May that triggers the emergence of adults.”
Wheat midge require 25 mm of cumulative rain in May to emerge from the soil where they overwinter. Dr. Wist predicts the 40 mm of rainfall Saskatoon received in late May will result in wheat midge activity and advises growers to be ready to scout as soon as wheat heads emerge, typically during the last week of June. “Start by setting up pheromone traps in the third week of June and brush up on what to watch for and how to scout for wheat midge to evaluate your thresholds.”
Understanding wheat midge thresholds
Wheat midge crop damage occurs during the larval stage. After hatching, the midge larvae feed on the developing wheat kernel, causing it to shrivel, crack and become deformed. The resulting loss of wheat kernels will lower yield and damaged kernels reduce quality.
Careful, regular monitoring of wheat fields between heading and flowering is necessary to identify wheat midge infestation thresholds and to evaluate any necessary action. Growers should monitor conventional wheat fields during the susceptible period – when the wheat head becomes visible as the boot splits until mid-flowering.
Starting with pheromone traps to monitor and collect adult midge wheat (males), growers can get detect pest pressure. Field scouting is necessary to identify females and determine thresholds.
Dr. Wist explains there are two thresholds to scout for – yield and quality. One female per five wheat heads (1 female/5 heads) meets a yield threshold, and one female per 10 heads (1 female/10 heads) indicate a quality threshold. “Only females sit on the heads, and they are bright orange, so they should be easy to spot,” explains Dr. Wist, reminding growers that diligent scouting is necessary.
Other handy wheat midge monitoring and prediction tools include social media. Dr. Wist encourages growers to follow the popular hashtag #MidgeBusters on Twitter for real-time updates from fellow growers across Western Canada. “We’re asking growers to share what’s going on in their fields, like when emergence starts, what thresholds they are seeing, and where they are. Sharing the info can help everyone.”
Growers can also request a pheromone trap and join the SeCan Midge Busters, an in-season monitoring network developed by Wist and SeCan that includes a What’s App group to report pest counts and share information with Canadian wheat growers. Use the QR code below to connect with SeCan Midge Busters.
Preventing wheat midge
Wouldn’t it be easier to just plant and forget about wheat midge? That’s what countless growers have done this year, planting midge tolerant wheat varieties.
With more than 35 midge tolerant varieties to choose from, growers can opt for peace of mind, while saving time and money. That’s something to think about if you find yourself spending your early summer evenings standing in your field, scouting for wheat midge.