Document Type

Thesis - Open Access

Award Date

2019

Degree Name

Master of Science (MS)

Department

Agronomy, Horticulture, and Plant Science

First Advisor

Adam Varenhorst

Keywords

Helianthus annuus, Melissodes trinodis, Pollinator, Yield

Abstract

In 2017 and 2018, South Dakota was the largest producer of sunflowers, Helianthus annuus L. (Asterales: Asteraceae) in the US, grossing approximately $178 million per year. In South Dakota, both confection and oilseed sunflower cultivars are grown. Despite breeding efforts to increase sunflower's ability to self-pollinate there is evidence that pollinator visitation results in increased sunflower yields. In addition, there is evidence that sunflower pollen is beneficial for pathogen resistance in various bee species, suggesting the importance of a mutualistic relationship between pollinators and sunflowers. In some areas, observed increases in sunflower yield is attributed to the presence of Apis mellifera (L.) as well as species of native bees. Annually, honey bee hives are moved to be within close proximity of sunflower fields. The effect that honey bees as well as other pollinators have on yield has been investigated in various crop studies including confection sunflowers. However, in South Dakota, the identity of the insect pollinators visiting sunflowers is unknown. Additionally, there is no evidence to suggest that oilseed sunflower production in South Dakota is positively impacted by the presence of pollinators. The objectives of this research were to identify the species of insect pollinators visiting South Dakota sunflower during flowering and determine if pollinator visitation positively impacted sunflower yield. This experiment was conducted at across four locations in South Dakota. The first location, Volga, SD was selected due to the absence of sunflower production in the area. The second, Onida (2016), third, Highmore, SD (2017), fourth, Gettysburg, SD (2018) and fifth, Pierre, SD (2018) locations were selected due to the large presence of sunflower production in the surrounding area. To explore these objectives 59 mL pan traps were modified by being painted with fluorescently dyed paint (i.e., bee bowls). After the onset of flowering, a cluster of three bee bowls were placed in the middle of sunflower plots at approximately 10:00 AM during sunny days with no forecasted precipitation and were removed 24 hours later. This procedure was repeated weekly until sunflower senesced. Each bee bowl contained a mixture of soap and water to capture the specimens. Once collected, specimens were cleaned using warm water, and then dried and stored until they were identified to the lowest taxonomic unit possible. Our results indicate that Melissodes trinodis Robertson was the most abundant pollinator at Volga, (2016), Highmore (2017) and both Gettysburg, and Dakota Lakes Research Station in Pierre, (2017 and 2018), while hover flies were the most abundant pollinators at the Volga (2017 and 2018) location. The pollinator community differed between locations and less than 5% of honey bees were observed across the years and locations of the experiment. We also observed that oilseed varieties on average yielded 26% greater when pollinators were not excluded. These results suggest that native pollinators likely play a more important role in sunflower production in South Dakota. This suggests that future studies should evaluate the impact that routine or contracted insecticide applications have on pollinator abundance, composition and their impact on yield.

Format

application/pdf

Number of Pages

89

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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