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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

Louis Hesler


Soybean [Glycine max (L.) Merrill (Fabales: Fabaceae)] has been grown in the United States since 1765 with few economically injurious arthropod pests. However, soybean aphids [Aphis glycines Matsumura (Hemiptera: Aphididae)] were first detected on soybean in the United States in 2000 and now cause an estimated monetary loss of up to US $4.9 billion annually. Many insecticides have since then been created for use against soybean aphid. However, other pesticides have exhibited efficacy against soybean aphid and this phenomenon is termed crossover activity. Crossover activity occurs when a pesticide at or near its label rate has activity against non-target pests. One product exhibiting crossover activity may be MilStop® (85% potassium bicarbonate), a broad spectrum foliar fungicide that is a registered organic product and has recently exhibited insecticidal properties, including efficacy against soybean aphid. The purpose of this study was to determine MilStop’s efficacy against soybean aphid in both growth-chamber and field-cage tests. In growth-chamber tests, MilStop, as a whole, directly reduced soybean aphid populations by 94%, 48 hours after treatment application, but MilStop’s active ingredient had no significant effect on soybean aphid populations. In field-cage tests, MilStop significantly reduced peak soybean aphid numbers per plant and cumulative aphid-days compared to water control. However, MilStop-treated soybean plant yield was not significantly different from the water control. Although MilStop’s efficacy against soybean aphid was demonstrated, further study is needed to determine application schemes, in which it can maintain soybean aphid populations below the economically injurious levels in soybean and to isolate the ingredient(s) of MilStop that are responsible for efficacy against soybean aphid.

Library of Congress Subject Headings

Soybean -- Diseases and pests -- Control Aphids Pesticides Fungicides


Includes bibliographical references (pages 132-133)



Number of Pages



South Dakota State University



Rights Statement

In Copyright