Document Type

Thesis - Open Access

Award Date

2025

Degree Name

Master of Science (MS)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Adam Varenhorst

Abstract

Although sunflowers are native to North America, the early breeding efforts to improve sunflowers occurred outside of the continent. These hybrids were reintroduced to North America around 1875. In the early 1900’s, efforts to increase oil content were achieved by selective breeding of the reintroduced hybrids. Although this resulted in the development of improved sunflowers, many of the traits that conferred resistance to native insect pests were lost. One insect pest, the red sunflower seed weevil was noted as having caused sunflower production to rapidly decline and eventually end in Illinois and Missouri. Unfortunately, red sunflower seed weevils are still a major insect pest of sunflower and commercial varieties confer resistance to this pest. In North Dakota and South Dakota, the red sunflower seed weevil causes considerable yield loss. Since 2017, researchers in South Dakota have received reports of pyrethroid field failures for red sunflower seed weevil management. Results from this study indicated that populations of red sunflower seed weevils in South Dakota are resistant to lambda-cyhalothrin, esfenvalerate, and cypermethrin. This poses a great challenge for red sunflower seed weevil management in South Dakota. The revocation of chlorpyrifos food tolerances in 2021 and again in 2024 has greatly reduced management options for red sunflower seed weevils. This leaves sunflower farmers in South Dakota with very few options, and heavy reliance on exemption labeled insecticides will occur. As a result of the red sunflower seed weevil pressure, sunflower acreage in South Dakota has declined in recent years, suggesting that red sunflower seed weevils may greatly reduce sunflower production in South Dakota.

Publisher

South Dakota State University

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Rights Statement

In Copyright