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2021 Wheat midge forecast map

By Jeremy Boychyn (M.Sc)(P.Ag), Agronomy Research Extension Specialist

Every year in the fall, provincial entomologists collect soil cores on wheat stubble across the province. The cores are then assessed for overwintering wheat midge (Sitodiplosis mosellana) cocoons. The data collected from this process is used to develop wheat midge risk maps.

The maps can be used by farmers to implement management decisions based on the risk of wheat midge. Wheat midge damage can be mitigated in a few ways. Firstly, Midge Tolerant Wheat (MTW) with the Sm1 gene can be seeded. MTW incorporates a non-midge tolerant wheat refuge to reduce the risk of developing a midge population resistant to the Sm1 gene. Secondly, is to control through scouting for wheat midge at heading and applying an insecticide registered to control midge when yield or quality thresholds are seen. Additionally, best management practices including high seeding rates and earlier seeding dates can create asynchrony (not occurring at the same time) between wheat midge egg-laying and wheat heading and anthesis timing (Collier et al., 2021).

The yield economic threshold for wheat midge is one midge for every 4-5 wheat heads. The harvested grain quality economic threshold is one wheat midge for every 8-10 heads.

For information of scouting techniques, see this informative video from Alberta Agriculture & Forestry.

The current and historic wheat midge forecast maps can be found on the Prairie Pest Monitoring Network (PPMN) website, here. The wheat midge forecast for 2021 (Figure 1) indicates areas of east-central Alberta are at elevated risk of midge pressure.

Figure 1: Wheat midge forecast map for Alberta and Saskatchewan 2021. 

Wheat midge requires around 25-30mm of rainfall in the spring to emerge from the soil and become a pest for the crop. Therefore, it is important to monitor ongoing environmental conditions. Accounting for environmental conditions, including rainfall, the PPMN provides weekly updates of predicted wheat midge development across the Prairies. The most recent update can be found here.

Using both the wheat midge forecast, the weekly development updates from the PPMN, and monitoring crop staging, producers and agronomists can stay ahead of wheat midge and manage them appropriately. 

References: 

Collier, G. R., Spaner, D. M., Graf, R. J., & Beres, B. L. (2021). Optimal Agronomics Increase Grain Yield and Grain Yield Stability of Ultra-Early Wheat Seeding Systems. Agronomy, 11(2), 240. https://www.alberta.ca/assets/documents/af-wheat-midge-forecast-map-2021.pdf