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Wheat Midge Update (07/09/20)

High temperatures continue to push insect development! The current accumulated degree days for wheat midge range from 1493 to 1764 in northern North Dakota, indicating that about 50-90 percent of females have emerged (see map).

High temperatures continue to push insect development! The current accumulated degree days for wheat midge range from 1493 to 1764 in northern North Dakota, indicating that about 50-90 percent of females have emerged (see map). If you are in a dry area, emergence could be delayed or even delayed until next year. Scouting for wheat midge is critical for wheat in the heading to early flowering stages, the susceptible crop stages. Please see Crop and Pest Report (Issue 8) for more information on scouting and map for wheat midge risk.

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If you scout fields and find wheat midge is above the Economic Threshold (hard red spring wheat = one or more wheat midge for every four or five heads; durum wheat = one or more wheat midge for every seven or eight wheat heads), and wheat is at the late heading to early flowering crop stages, insecticides can be effective for reducing the adults and larvae (Figure 1). Insecticides applied at 30% heading were not effective in reducing wheat midge populations (Figure 1) and growers should wait about 4 days before an insecticide application. Insecticides applied at late flowering (>50% flowering) also are not recommended (Figure 1) since most of the larvae are protected within the glumes and wheat is no longer attractive to the adult wheat midge for egg laying. In addition, parasitic wasps emerge after the wheat midge and a late flowering insecticide application will have a negative impact on their populations, reducing natural biological control of wheat midge.

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The optimal timing for insecticide application is recommended at dusk because female adults are most active in the top of the crop canopy. Apply in a minimum of 3 to 5 gallons of water per acre for aerial applications and 10 gallons of water per acre for ground applications. Insecticides labeled for wheat midge can be tanked-mixed with fungicides for Fusarium head blight (or scab) control during early flowering.

Janet J. Knodel

Extension Entomologist

 

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