Date of Graduation


Document Type


Degree Name

Bachelor of Science in Agricultural, Food and Life Sciences

Degree Level



Crop, Soil and Environmental Sciences


Rojas, J. Alejandro

Committee Member/Reader

Egan, Martin

Committee Member/Second Reader

Chilvers, Martin, I.

Committee Member/Third Reader

Savin, Mary C.


Cercospora spp. and Corynespora spp. are two common foliar fungal pathogens in Arkansas amongst other soybean producing areas. Two primary diseases caused by Cercospora spp. are Cercospora Leaf Blight (CLB, caused mainly by C. kikuchii) and Frogeye Leaf Spot (C. sojina). Both diseases affect foliage, and when lesions collapse, leaves may fall prematurely resulting in yield loss. In the specific case of CLB, this is a disease on the rise since 2000, and also causes seed infection reducing seed quality. Target spot is a disease caused by Corynespora cassiicola, and is of less damaging for farmers in larger soybean producing countries like the US, however disease incidence has been increasing overtime. However, Target Spot has still caused significant harm to plants when left unchecked. Over time, many fungicides used to combat these diseases have become ineffective as the pathogens have developed a resistance to them. The mode of action of the fungicides in question are Quinone Outside Inhibitors (QoIs – FRAC 11) and Triazoles (DMIs – FRAC 3). The primary goals of this research project were to establish a collection of Cercospora spp. and Corynespora spp., establish a method for testing fungicide resistance determining EC50 (Effective concentration at 50% growth) using fungicide levels 0.01, 0.1, 1, 5, 10, and 50 mg/L, and establish a baseline of resistance against the two chemistries to determine resistance in the field.


Cercospora, Corynespora, Soybeans, Fungicide Resistance