The wheat midge forecast for 2021 shows an increase in wheat midge risk in central Alberta. Risks in the Peace River Region remain low but should not be underestimated going into 2021 cropping year. It is important to note that there are sufficient populations of midge to fuel a resurgence if conditions are in the insects favour (specifically delayed crops and higher than normal rainfall).
The area in central Alberta east of Edmonton has developed into a high risk situation. Producers in that area should be considering midge tolerant wheat and other integrated pest management (IPM) strategies to minimize this risk. Wheat midge in both areas will remain a concern in individual fields, especially if there is late seeding and higher than average rainfall in the spring.
Areas west and south of Edmonton have also seen individual fields with midge numbers at levels of concern as far south as Starland County. The population remains low in southern Alberta.
Over the past several years, the field-to-field variation has been considerable throughout the province. Individual fields throughout Alberta may have economic levels of midge. Each producer needs to assess their risk based on indicators specific to their farm. Specifically, producers should pay attention to midge downgrading in their wheat samples and use this as an indication of midge risk in their fields.
The 2020 fall survey included wheat growing areas throughout Alberta. In total, 311 samples were taken from 64 counties. The survey involves taking soil samples from wheat fields after harvest using a standard soil probe. Larval cocoons are washed out of the soil using a specialized series of screens. Larvae are counted, and then dissected to determine parasitism levels in the midge. The midge density displayed on the forecast map is based on viable (live, non-parasitized) midge larvae.
Wheat Midge Forecast 2021 (map) - (PDF, 4.1 MB)
This forecast is not intended to take the place of individual field monitoring. The forecast for Alberta shows areas of risk for midge damage in 2021. It is important to note that over such a wide range, populations in individual fields can be and often are highly variable. Producers should plan to monitor their fields when the midge adults are flying and their wheat is in the susceptible stage. In all areas of the province growers are urged to monitor their wheat fields from wheat head emergence to anthesis for the presence of midge adults. Regular field scouting on multiple nights in succession is important in understanding the population in a particular field.
Although a number of factors influence the overwintering survival of the midge, the survey and map provide a general picture of existing densities and the potential for infestation in 2019. Weather conditions, specifically temperature and moisture will ultimately determine the extent and timing of midge emergence during the growing season. Temperature and wind also play critical roles in egg laying activities of the adult female wheat midge. The level of damage from wheat midge is determined by the synchrony of wheat midge emergence and wheat and the number of wheat midge present. Look for the results of our wheat midge pheromone trapping in June and July to help track adult midge emergence.
Parasitism of midge larvae by a small wasp species (Macroglens penetrans) has been important in keeping wheat midge populations below the economic threshold in many areas. These beneficial wasps tend to thrive in warm, dry conditions. Parasitoid populations increase and decrease with changes in the midge population and are very important in moderating population levels in Alberta. Parasitism levels in the 2020 survey samples were very low.
It is important to understand that once midge has established in an area it unlikely to ever completely disappear. Low-lying and moist areas in fields provide a refuge, enabling the population to survive even when conditions are not favorable in the rest of the field. These low population levels, however, also help sustain a population of natural enemies.
The wheat midge survey was conducted by Alberta Agriculture and Forestry with assistance from:
- Battle River Research Group
- Chinook Applied Research Association
- County of Two Hills
- Farming Smarter
- Gateway Research Organization
- Lakeland Applied Research Association
- Mackenzie Applied Research Association
- MD Wainwright
- Mountain View County
- Northern Peace Applied Research Association
- Parkland County
- Smoky Applied Research and Demonstration Association
Agriculture and Agri-Food Canada’s David Giffen produced the map. Thank you to Alberta Agriculture and Forestry’s Brennan Folkerts for your contribution to the soil sampling this fall.