Entomology, Department of
First Advisor
Dr. Jeffrey Bradshaw
Second Advisor
Dr. Autumn Smart
Date of this Version
8-2023
Abstract
Sunflower (Helianthus annuus) is cultivated for oil and seed production worldwide, and the United States produces 2.5% of the world’s oilseed sunflower primarily grown in the Great Plains. In 2022, oilseed and confectionary U.S. sunflower production increased by 48 and 44%, respectively, compared to last year's records. However, sunflower production can be seriously compromised by insect pests. The red sunflower seed weevil (Smicronyx fulvus LeConte) is considered the most serious pests in North America and causes severe economic damage yearly. On the other hand, native bees contribute substantially to sunflower yield. Currently, insecticide applications are the primary tool to suppress red sunflower seed weevil (RSSW) populations during sunflower bloom. However, the impact on native bees and their pollinator services has not been documented. A study was designed to examine the impact of planting date on red sunflower seed weevil population control as well as the impact of insecticide application timing on native bees and their pollinator services. The results from this study indicated that planting date is irrelevant to RSSW control since insecticide application effectively suppressed RSSW populations. Additionally, insecticide applications did not impact bee visitation rate or pollinator services. A separate study evaluated the effects of differing insecticide application strategies to control RSSW populations, focused on reducing overall insecticide input in the agricultural system and evaluating a strategy for insecticide reduction on native bee populations and their value to sunflower yield. Results indicated that insecticide applications only of field borders provided equivalent RSSW control and facilitated higher bee visitations relative to fields with 100% treated acres. Additionally, pollinator services were not impacted by any insecticide application strategy. Restricting insecticide applications to field borders can protect the crop with lower economic cost and environmental impact, and aid in supporting wild bee communities.
Advisor: Jeffrey Bradshaw and Autumn Smart
Comments
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Entomology, Under the Supervision of Professors Jeffrey Bradshaw and Autumn Smart. Lincoln, Nebraska: August 2023
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