Wheat midge – Survey and maps

This is not a forecast. It is a summary of the situation in Alberta in 2024.

Overview

The wheat midge survey results are positive for 2024. Midge population is low across the province. The field in Cypress County with <600 midge was an irrigated field.

Keep in mind, wheat midge can remain as a diapausing larva in the soil for at least one cropping year. A resurgence of the population can occur if there is a higher than normal rainfall in May and June.

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. Even though the map may indicate that there is not a risk for midge in a specific area, that does not mean that there is no risk.

In 2024, the wheat midge pheromone trapping network indicated high adult midge numbers in June and July. This network is very helpful in indicating when the midge are emerging from the ground. These traps are an effective tool in the planning of wheat midge scouting, but do not indicate the levels of infestation.

Keep in mind, even if you are in the green areas of the map, wheat midge could still be an issue if weather conditions favour their development.

For information on identification, life cycle, damage and pest management, see Wheat midge – Overview.

Methodology

The growing season in parts of southern Alberta was dry in 2024. With that in mind we only surveyed irrigated fields in Cypress and Forty Mile Counties, and a reduced number of survey locations in Special Areas 2 and 3.

In total, 265 samples were taken from 60 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.

2024 survey findings

Wheat Midge Survey Map 2024

This map is not intended to take the place of monitoring populations in individual fields as populations of this insect 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, from the boot crack until anthers are visible on the heads.

Regular field scouting on multiple nights in succession is important in understanding the population in a particular field. Look for the results of our wheat midge pheromone trapping in June and July to help track adult midge emergence.

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 2025. 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.

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.

Acknowledgements

Thank you to those who assisted with the wheat midge survey:

Mountain View County
Parkland County
MD of Wainwright
Alberta Plant Health Lab Survey Technicians

Thanks to all the agronomists and Agriculture Fieldmen who lined up fields and to the producers who offered their fields for the survey.

Thanks to Jon Williams from Agriculture and Agri-Food Canada for producing this map.

AI search tool

Popular topics: