By Scout Nelson
The red sunflower seed weevil, a small but formidable pest, poses increasing threats to sunflower crops, particularly in South Dakota. Patrick Beauzay, a research specialist and integrated pest management coordinator at North Dakota State University, reports significant challenges due to the weevil's confirmed resistance to pyrethroid insecticides.
During the annual cycle, female weevils commence by feeding on pollen and progress to laying eggs inside sunflower heads around the R 5.3 growth stage.
The larvae from these eggs can devour up to one-third of the sunflower kernels, with severe cases seeing 50% to 80% seed infestation, drastically reducing seed weight and overall yield.
In 2023, surveys across 35 counties in North Dakota detected the pest in 169 fields, though few reached critical levels. Unlike North Dakota, South Dakota faces more severe infestations, partly due to the pest's growing resistance to pyrethroids, a problem first noted in 2017.
Research efforts have concentrated on evaluating the interaction between planting dates and insecticide efficacy. Experiments at various research farms in both Dakotas employed multiple insecticide treatments, including newer products like Plinazolin by Syngenta, which shows promise due to its different mode of action. This new insecticide has proven effective against resistant weevil populations in both wheat and sunflower trials.
Beauzay and his team continue to explore alternative strategies to combat this pest, emphasizing the importance of timely and effective management practices to sustain sunflower production and protect crop value.
Categories: North Dakota, Crops