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Wheat Stem Sawfly Numbers Up in the Panhandle
By: Jeff Bradshaw, UNL Extension - 06/11/2018

Early insect surveys in the Nebraska Panhandle indicate higher populations of wheat stem sawflies than in recent years in some areas. While it isn't entirely clear as to what might be causing the increase this year, we have noted a slow but persistent spread of the intensity of infestation over the past few years as its range has extended from the northern Panhandle southward and as far east as Chapell. Many variables, such as soil management, variety, crop rotation, and temperature, affect populations.

This student video shows wheat stem sawfly activity in wheat on May 25 near Gurley. We found over 200 adult sawflies per 20 sweeps in that field. We returned to the same field on May 30 to still find around 130 adult sawflies per 20 sweeps. This is the highest population of sawflies that we have documented in this area of the southern Panhandle since we begin surveying for this insect eight years ago.

The wheat stem sawfly (Cephus cinctus Norton) is brown with yellow legs and approximately 1/2 inch long. Severe infestations can cause widespread lodging in a field and complicate harvest (Figure 1). While there are no in-season control measures, planting solid stem varieties this fall may lessen damage due to lodging in next year's crop.

Extension colleagues in Colorado have indicated they are seeing similar large populations of this insect in northeastern Colorado.

University of Nebraska-Lincoln student Bethany Bergstrom is currently conducting a wide survey throughout western Nebraska wheat fields, grasslands, and pastures to evaluate grass hosts for the wheat stem sawfly and its parasitoids. Previous surveys have documented found wheat stem sawfly larvae present in downy brome, intermediate wheatgrass, Japanese brome, smooth brome, and rye.

Bergstrom recently collected an adult wheat stem sawfly from a grassland area north of Ashby, just nine miles west-northwest of Hyannis. This sample would likely represent the furthest east that the wheat stem sawfly has been collected in Nebraska since the 1940s. Results from the survey will be reported later in CropWatch.

See Wheat Stem Sawfly in Wheat, a 2016 webinar on the Plant Management Network by Jeff Bradshaw. It addresses the insect's life cycle, geographic range, host range, how it causes damage, and control options.

For management recommendations see: Cultural Management Options for Wheat Stem Sawfly in CropWatch.

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