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Oral Presentation
Oral Presentation
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Student Poster Display Competition

Plant-Insect Ecosystems

Student Competition

Student

Undergrad Poster Competition: P-IE, IPM

D3170: A novel method for augmentative biological control for wheat stem sawfly management in Nebraska wheat

Monday, November 10, 2025
9:00 AM - 5:00 PM Pacific
Location: Exhibit Hall A-A1, OCC
Poster Display Student Competition
The wheat stem sawfly (Cephus cinctus Norton) is an increasingly significant pest in wheat across the Northern Great Plains. Larval feeding within the stem creates a V-shaped notch at the stem base, which weakens plants, causing lodging and yield losses. Infestation in Nebraska began in the mid-1990s and has since spread south and eastward. Available control methods, including resistant wheat varieties (e.g., solid stem), tillage, and swathing, are either insufficient or not preferable. This study evaluated a novel method for augmentative biocontrol strategy using parasitoids Bracon cephi and B. lissogaster to reduce sawfly population and damage. Wheat straw harboring parasitoids was baled, transported, and unfurled at eight sawfly-infested wheat fields in western Nebraska. Before releasing parasitoids, wheat stubbles from adjacent wheat fields were sampled to gauge sawfly pressure and detect local parasitoid presence. Wheat stems were collected before harvest to estimate sawfly and parasitoid abundance. On average, 26 parasitoids were recovered in 500g of straw. After releasing parasitoids on the field edge, three fields showed decreased cutting by 2-10%, while cutting was increased in five fields by 3-33%. Sawfly infestation rate was high in most fields. However, percent cutting was low when parasitism rate was high and vice versa. Sawfly infestation rates were lower, but parasitism rates were higher 50m inside the field than on the edge. Overall, our study demonstrated that straw-mediated parasitoid releases are effective. Sawfly and parasitoid abundance will be monitored in the next wheat crop to evaluate parasitoid establishment and reduction of sawfly infestation.