Theses and Dissertations

Issuing Body

Mississippi State University


Irby, John T.

Committee Member

Catchot, Angus L.

Committee Member

Allen, Thomas W.

Committee Member

Maples, William E.

Committee Member

Pieralisi, Brian K.

Date of Degree


Document Type

Graduate Thesis - Open Access



Degree Name

Master of Science (M.S.)


College of Agriculture and Life Sciences


Department of Plant and Soil Sciences


Soybean growers in the southern United States commonly deal with disease issues that can limit yield potential. As a result, growers have adopted prophylactic fungicide application targeted at specific growth stages as a standard management practice. However, yield responses to prophylactic applications have become sporadic over time. One major change that has occurred is adoption of cultivars with improved disease tolerances. Therefore, the objective of this research was to evaluate yield response of cultivars representing multiple genetic backgrounds to fungicides applied prophylactically at the R4 soybean growth stage. Experiments were conducted in 2020 and 2021 to determine the yield impact of prophylactic fungicide applications in MG IV or V cultivars across different planting dates and multiple soil textures. A yield increase was observed for soybean treated with a fungicide compared to nontreated soybean. However, a yield response between nontreated and treated soybean within cultivar was not observed, indicating that differing cultivar disease tolerances may not influence soybean yield response to prophylactic fungicide application.