Figure 1. Top view of a wheat stem maggot adult. Courtesy: Patrick Beauzay, North Dakota State University.
Wheat stem maggot adult activity has been observed in winter wheat fields in South Dakota. Researchers at SDSU Extension are working collaboratively with researchers from North Dakota and Nebraska to determine peak wheat stem maggot adult flights. Although the adults don’t cause significant injury, the larvae of the wheat stem maggot cause white or bleached wheat heads later in the season. Wheat that is damaged by the wheat stem maggot results in a white/dry head and stem to the first node where the flag leaf is attached.
The wheat stem maggot adults are small yellow flies (1/5 inch long) with bright green eyes. Adults have three black stripes present on their thorax, with the middle stripe longer than the other two (Figure 1). Magnification may be required for identification. Adults also have a segment on their head that extends forward beyond the eyes. Adults of the wheat stem maggot are nectar feeders and lay eggs on the leaves and stems of wheat plants. When the eggs hatch, the larvae burrow into the stem and begin feeding near the flag leaf. This feeding prevents nutrient flow to the head. Although a wheat field may have many white heads due to wheat stem maggot feeding, it is still considered a minor pest and chemical management is not recommended.