Evaluating trade-offs between pest management and pollination and sunflower yield in Nebraska

Sunflower, Helianthus annuus L. (Asterales: Asteraceae), is endemic to the United States and is cultivated in the Great Plains for seed and oil production. Seed quality is affected by a key insect pest, the red sunflower seed weevil (Smicronyx fulvusLeConte), which is effectively and routinely managed using insecticides. However, insecticide use can also impact bee populations and their pollination services, potentially influencing yield. Sunflowers are largely self-pollinated, however, insect-mediated pollination can increase yield. The interaction between insecticide application, pest control, and bee pollination in sunflowers is not well documented. To evaluate this interaction and to explore management strategies, on-farm field trials were established in 2021 on 15 commercial sunflower fields in western Nebraska. Our experiment had four treatments (and two replicate fields per treatment) that were deployed based on the insecticide-treated area during sunflower anthesis: Conventional application – 100% of field treated (CA), border application (BA), early-blooming border application (EBA) and untreated control (UC). Pest incidence was not statistically different for CA, BA, and EBA, but they all had fewer weevils per head than the UC. Bee visitation rates for BA and EBA were higher compared to CA and UC.
Moreover, bee abundance, richness, sunflower injury, and yield were measured. Results indicate that border applications may be as effective as conventional applications for pest suppression. Further, bee visitation rates are affected by treatments and may impact seed sets. These results will help growers and pest managers reduce insecticide input and maximize yield while conserving bee populations in Nebraska.