WSS Overview and Resources:
Wheat stem sawflies (Cephus cinctus Norton, WSS) pose a severe threat to CO wheat production. See below for useful documents and other resources regarding this pest.
WSS Fact Sheet: This document is a good starting point for growers seeking to learn more about this pest.
2025 WSS FAQ: This document answers common questions about the WSS lifecycle, damages to wheat crops, and management practices.
2025 WSS Statewide Survey: This report covers our 2025 estimate of WSS infestation in Colorado. Please note that infestation can expand beyond the hotspots shown here, given our limited sampling time each season. Maps from previous years can also be found in the PowerPoint file below:
| WSS maps 2013-2025 |
WSS Phenology Model: This model was created by Dr. Henrique Vieira, our former PhD student. Growers can use it to predict when they will see peak sawfly emergence in their area. Instructions for using the model are listed below:
- The model is available here.
- Click on the "Station" tab at the top of the page. Use the search feature to find the weather station closest to your operation. Select your preferred station from the list of available options.
- Select the "Model" tab at the top of the page.
- In the "Model" drop down menu (located below "Model category") select "wheat stem sawfly (Colo St. Univ. 2025)" from the list of options.
- Set the temperature scale to Celsius.
- Click on the "Output" tab at the top of the page.
- You will see a results table with dates for the expected beginning, peak, and end of the sawfly flight. These dates will be updated whenever your weather station records more growing degree day data.
Example output page for phenology model, note that peak WSS emergence is projected on May 15, 2026. This date will update as more degree day data accumulates.
Additional Resources: See below for other good places to find WSS updates, management strategies, etc.
- Colorado Wheat hosts our newsletters and provides regular updates on wheat crops.
- The USDA-ARS research hub can be accessed here. Searching "sawfly" will bring up a list of relevant articles.
- "CROPWATCH" from UNL provides contacts for wheat specialists and posts findings on WSS research. It can be found here.
- Access the Extension homepage for MSU here. Use the search feature in the top righthand corner to find sawfly-related content.
