Wheat Midge Outlook - Does This Affect You?

In Manitoba, the conversation about wheat midge has been fairly limited, since it is not yet a prevalent pest in the majority of fields in the province. However, there is significant damage occurring in Alberta and Saskatchewan. Wheat midge can thrive wherever wheat is grown, so we can assume that the migration of this pest into Manitoba is inevitable. However, there are no forecast maps available for our province yet.

Here's how a wheat midge infestation could impact your wheat crop:
The way that midge feed on the crop has a primary impact on the grain grade and a secondary impact on the grain yield. The Yield Threshold given by Dr. Tyler Wist is 1 adult midge per 5 wheat heads compared to the Grade Threshold of 1 adult midge per 10 wheat heads.

30% kernel infestation (kernels NOT wheat heads) can generate roughly 40% yield loss! So, it is very important to stay on top of scouting for this pest and using the best preventative measures available.

Tips for scouting and managing wheat midge:
Wheat Midge are occasionally called the “Canada Day Pest”, since this is the time of year when adult midge emerge. The optimal time to scout is just prior to Canada Day at sunrise/sunset when there is low wind – these are the optimal conditions for adult midge to lay eggs in the wheat heads. Male adults emerge about 2-3 days prior to the females – this allows us to use pheromone traps to monitor the emergence of the pest in an area (these traps indicate presence of the pest NOT pest pressure). Each female midge will lay about 80 eggs within their 1-week lifetime. Those eggs hatch into larvae which live on the wheat head and feed for about 2-3 weeks until crawling down the stem to overwinter in the soil (Only 1 generation per year).

Using an insecticide in-season would be a last-resort recommendation, likely only used in extreme cases. The window to spray for these pests is very narrow and late in the season. Using an insecticide for control would also impact the beneficial parasitoids that show up after the eggs are laid.

The most effective control measure that can be applied on farm is the use of midge tolerant wheat varieties (29 different varieties available with tolerance). These red spring wheat varieties naturally carry a SM1 gene which allows tolerance to wheat midge. However, there is risk of the wheat midge becoming resistant to this single trait. In order to protect this sole protection gene, a stewardship program was developed. All midge resistant wheat varieties are blended with 10% of a susceptible variety. The ability for wheat midge to genetically overcome the SM1 gene is recessive, therefore using a refuge of a susceptible wheat variety, and reducing the exposure of the SM1 gene to the midge population works as a preservation method for this control measure.

Quick Economic note:
Manitoba Crop Alliance and Dr. Tyler Wist provided a cost evaluation in the most recent Wheat Midge Outlook meeting. Dr. Wist’s numbers show that if you consider a risk of 15% damage by wheat midge, current average wheat yields and commodity prices, using a midge tolerant variety can keep up to $94.50/ac in your pocket in the event of increased wheat midge pressure in your fields.

In order to build forecast maps for Manitoba there is a need to expand the network of pheromone traps across the province. If you are willing to have a pheromone trap in your fields please reach out to us at Pitura Seeds and we can help facilitate this for you. Or reach out to Dr. Tyler Wist for more information about how you can contribute to his forecasting (tyler.wist@agr.gc.ca)

~Katie Meggison