Degree Type


Date of Award


Degree Name

Master of Science





First Advisor

Erin W. Hodgson

Second Advisor

Matthew E. O'Neal


Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), has been a prominent insect pest in the northcentral region since 2000. Insecticides are the primary management tactic for this pest, but some populations of soybean aphid resistant to pyrethroid insecticides have been reported since 2015. This increases the impact of soybean aphid on soybean, Glycine max (L.) Merr (Fabales: Fabaceae), production, which is already challenged by higher input costs, declining market value, and unpredictable weather. Soybean aphid-resistant varieties are available to farmers but limited to genetic backgrounds that exclude herbicide-tolerance. This is a significant barrier to adoption since farmers rely on herbicide-tolerant varieties for convenient weed control. We hypothesized that the value of aphid-resistant varieties will vary depending on the environment, aphid-resistant varieties provide better yield protection than insecticide applications, and insecticide-resistant aphids will further reduce profit margins for soybean farmers.

To test these hypotheses, plots were established in 2016 and 2017 at two locations in Iowa that varied in their risk for an aphid outbreak. Planting date was varied at these locations to mimic different yield environments. Aphid populations were recorded weekly and plots were harvested for yield data. We then performed an economic analysis of the soybean-soybean aphid system in Iowa. Results from the field experiment were incorporated into the analysis as assumptions or components of the model. The model was used to predict how expected yield and expected net revenue are affected by farmer decisions related to management of soybean aphid outbreaks that may contain insecticide-resistant soybean aphids.

Copyright Owner

Ashley Nicole Dean



File Format


File Size

151 pages

Included in

Entomology Commons