We will evaluate the impact of insect pest populations on soybean yields while assessing the return-on-investment of common pest control tactics used by Illinois soybean farmers.

To make more informed pest management recommendations, farmers need to know (1) how often the controls they use can be expected to provide a positive return on investment and (2) the population density various insect pests must reach before a control is economically justified. We propose to address these knowledge gaps using simple field experiments placed both on University of Illinois research farms and on fields managed by cooperating farmers. We will apply pest controls that are commonly used as a preventative tactic by Illinois farmers, including insecticide seed treatments and foliar applications of pyrethroids targeting reproductive growth stages, and compare them with untreated plots. We will then thoroughly document insect population densities, yield, and other agronomic characteristics. By placing multiple trials throughout the state, we will observe both the frequency at which these inputs provide a positive return on investment and, when they do, the insect species most responsible for reducing soybean yields in Illinois.

• The results will provide an assessment of the return on investment for the most common insect control tactics used in Illinois soybean production.
• Our thorough assessment of pest populations will allow us to determine the relationship between insect pest populations and soybean yield in a field setting.
• This project will form the basis for a graduate student thesis or dissertation, providing training for the agricultural research sector in Illinois
• Long-term: this series of experiments will allow us to develop more accurate economic thresholds for insect management.

Farmers will have an improved assessment of return on investment of insect control practices in soybean in Illinois and a better understanding of the relationship between pest populations and soybean yield loss.