Wheat Stem Sawfly Emergence — Field Notes from Early June

Wheat stem sawfly
An adult wheat stem sawfly in wheat at the High Plains Ag Lab.

Wheat Stem Sawfly Emergence — Field Notes from Early June

The wheat stem sawfly has begun emergence throughout the High Plains. Observations from the High Plains Ag Lab (HPAL) near Sidney, Nebraska, the USDA-ARS Research Station in Akron, Colorado, and as far east as Deuel County, Nebraska indicate very high populations of wheat stem sawfly in wheat fields. Additionally, as one walks wheat fallow fields, you can also find wheat stem sawflies flitting around the residue, regardless of what the annual crop might be. This is because the wheat stem sawfly survives from mid-July through May in the pupal stage within wheat residue left behind from the previous harvest.

A swarm of adult wheat stem sawflies in wheat at the High Plains Ag Lab. (Video by Jeffrey Bradshaw)

Observations this week at HPAL indicated that sawflies might be emerging from deep within fallow fields and not just emerging from field edges. This pattern of emergence suggests a very large population at that location. This is certainly not good news for wheat producers in the southern Panhandle, who witnessed striking wheat lodging in some fields last year that resulted from heavy sawfly infestations.

The silver lining, at least for HPAL, is that as a test site for the State Variety Test, we will have an opportunity to compare wheat varieties under high sawfly infestations. This may help “ground truth” current sawfly resistant varieties as well as help us gain new insights into sawfly resistance. Additionally, the Small Grains Breeding Program at UNL has sawfly resistance as one of their primary breeding objectives. Lastly, we have provided an overview of tillage practices and possible parasitoid conservation efforts that may play a role wheat stem sawfly population dynamics and their management.

So what can a wheat grower do now? If you believe that your infestation will result in losses close to or below your crop insurance guarantee, turn in a probable loss claim with your crop insurance agent now.

However, from a production standpoint, there is not much you can do. We will discuss options for producing wheat under threat from the wheat stem sawfly in a later CropWatch article.

We also recommend trying to gather information about which of your acres seem to have the highest sawfly infestations and be timely in harvesting heavily infested fields. As your wheat fields begin to ripen, consider cutting some handfuls of wheat at a few locations across your wheat fields, split 25-50 handfuls of tillers and observe any tillers with frass or “sawdust” within the tillers. No other insect that infests wheat will leave behind frass within the tillers, which will otherwise be mostly hollow (unless you planted a solid-stem variety). Take notes on where and which fields you find sawfly infestation and this may give you insight for what you could do this coming fall or spring to manage your fallow for sawfly, or help you make decisions for variety selection or winter crop choice this for this fall.

You can help us learn more about wheat stem sawfly in our region if you share your sawfly observations with us, so please send your field updates to Jeff Bradshaw to help us learn more about wheat stem sawfly infestations. I’ll compile these notes and share them back out to our dryland cropping systems community this fall.

Keep an eye on CropWatch this summer as we keep track of the progression of this very important wheat pest and as we hopefully are able to glean some additional information to report from this year’s infestations.