Document Type

Thesis - Open Access

Award Date

2019

Degree Name

Master of Science (MS)

Department

Agronomy, Horticulture, and Plant Science

First Advisor

Adam J. Varenhorst

Keywords

aphid resistanc, below ground insects, insect feeding, neonicotinoid, Pyrethroid reistance

Abstract

The utilization of cover crops and no-till practices are important for the conservation of both soil and moisture in South Dakota. However, it is unknown if these practices impact the efficacy of insecticide seed treatments. In soybean, insecticide seed treatments are used prophylactically to prevent potential crop losses from early season insect pests. The prophylactic use of any management strategy increases the likelihood for selection pressure and also represents unnecessary input costs. The purpose of the research conducted for Chapter 2 was to determine the impact that tillage systems, cover crops and planting populations have on the efficacy of insecticide seed treatments. Two years of field data was collected from established long-term tillage and cover crop rotation plots at the South Dakota State University Southeast Research Farm. During each year, four factors were evaluated for their impact on yield (i.e., tillage, cover crop, seeding rate and seed treatment). Stand counts, soil samples and yield data were taken from each plot. In Chapter 3, we evaluated pyrethroid resistance in soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae) populations in South Dakota. In 2015, the University of Minnesota discovered populations of the soybean aphid that were partially resistant to pyrethroid insecticides. Due to the soybean aphid’s capacity for rapid reproduction and its ability to travel long distances in its alate (i.e., winged) form, it was determined that South Dakota may have resistant populations present. In 2017 and 2018, an efficacy study was deployed at three locations, over two years throughout Eastern South Dakota. A total of eight foliar insecticides were used in 2017 and 10 foliar insecticides in 2018. The results from chapter 2 indicate that seed treatment and cover crops have no significant impact on soybean yield. The results from chapter 3 determined that pyrethroid resistant soybean aphids are present in South Dakota.

Publisher

South Dakota State University

Rights

In Copyright - Non-Commercial Use Permitted
http://rightsstatements.org/vocab/InC-NC/1.0/

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