Theses and Dissertations

Issuing Body

Mississippi State University


Poston, Daniel H.

Committee Member

Blaine, M. Alan

Committee Member

Sciumbato, Gabriel L.

Committee Member

Price, James A.

Date of Degree


Document Type

Graduate Thesis - Open Access



Degree Name

Master of Science


College of Agriculture and Life Sciences


Department of Plant and Soil Sciences


Field studies were conducted in 2003, 2004, and 2005 in the Mississippi delta at 12 locations across common production practices to evaluate the impact of 12 single applications of fungicides at the R3 and R5 growth stage on soybean yield, seed quality, and net returns. Averaged across locations, azoxystrobin alone and mixed with other fungicides increased yields 161 to 343 kg/ha compared to the nontreated control. Fungicide applications made at R3-R4 were more efficacious and resulted in larger yield increases than applications made at R5-R6. Plots treated at the R3-R4 growth stage with 0.11kg ai/ha azoxystrobin alone or in combination with other fungicides yielded 135 kg/ha more than plots treated with the same treatments at the R5-R6 growth stage. Azoxystrobin at 0.11 kg ai/ha and azoxystrobin at 0.11 kg ai/ha + 0.035 kg ai/ha diflubenzuron were the most profitable treatments and increased net returns $23/ha and $31/ha, respectively compared to the nontreated control.