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Document Type

Thesis - University Access Only

Award Date

2015

Degree Name

Master of Science (MS)

Department

Biology and Microbiology

First Advisor

Johnathan Lundgren

Abstract

Sunflowers (Asterales: Asteraceae, Helianthus annuus) are an important oilseed crop grown worldwide. Cultivated varieties grown today have close ancestral ties to wild sunflowers native to North America. The long coevolutionary history between arthropods and this crop has resulted in a complex community of beneficial and pest organisms relying on the resources provided by these plants. Producers have almost ubiquitously adopted neonicotinoid seed treatments to manage pests, but the non-target effects on beneficial organisms, and the ability to reduce herbivores and increase crop yield is questionable. Here, I assess the foliar and subterranean arthropod communities over three site years in sunflower fields of central and eastern South Dakota, and describe how a seed treatment affects predators, herbivores, pollinators and yield. Persistence of thiamtheoxam and its metabolite clothianidin within plant tissue was also monitored. Sunflowers host a large diversity of arthropods, totaling 467 morphospecies from 19 orders beneath the soil’s surface and 15 orders in the foliage and flowers. Fewer aboveground predators and pollinators were found in fields treated with a thiamethoxam seed treatment, but foliar herbivores, and subterranean predators and herbivores did not differ between treatments. Within the foliar predatory guild, predaceous Coccinellidae were reduced in fields receiving a seed treatment. Thiamethoxam was present in viii sunflower tissue until the R1 plant stage, while clothianidin persisted throughout flowering (R6). Across site years, there were no yield benefits associated with the seed treatment. The use of a neonicotinoid seed treatment in this study provided a risk to beneficial arthropods while failing to suppress herbivores or improve crop yield. Future research should be aimed at developing integrated sunflower pest management strategies which promote herbivore control via natural biological factors and rely less on agrochemical inputs.

Library of Congress Subject Headings

Neonicotinoids--Physiological effect
Insecticides--Physiological effect
Arthropoda--South Dakota
Sunflowers--Effect of pesticides on
Seed treatment.

Description

Includes bibliographical references (pages 70-78)

Format

application/pdf

Number of Pages

99

Publisher

South Dakota State University

Rights

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

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