D3478: Surveying for wheat stem sawfly in South Dakota

Wheat, Triticum aestivum L., is one of the major cereal crops grown worldwide. Around 20% of yield loss in wheat is due to biotic stress factors, including insect pests. One of the contributors to wheat yield loss in the Northern Great Plains is the wheat stem sawfly. Wheat stem sawfly larva bores into wheat stems, causing yield loss and lodging. Previous studies suggest that the distribution of wheat stem sawflies in South Dakota is limited to the northern counties within the state. However, reports during 2022 suggested that wheat stem sawfly may be more widely distributed within South Dakota. To determine the actual distribution of wheat stem sawfly in South Dakota, a two-year survey was conducted. During the 2023 survey, 1-4 wheat fields in each county were surveyed. Due to the low detection of wheat stem sawflies in 2023, the 2024 survey was conducted in 25 of the 66 counties in South Dakota. During both years, fields were surveyed from June through mid-July. Sampling was conducted in each field using four transects, with sampling points on each transect occurring at 3, 30, 60, 90, and 120 feet, respectively, from the edge of the field using a sweep net. Wheat stem sawflies were collected from Harding and Perkins Counties in 2023 and Harding County in 2024. The results of this survey refute the 2022 reports and indicate that farmers outside of Harding and Perkins Counties can effectively use hollow stem wheat varieties.