Master of Science (MS)


Plant Pathology and Crop Physiology

Document Type



Cercospora leaf blight (CLB) of soybean caused by Cercospora kikuchii is an important disease in Lousiana. Preliminary screening of foliar applications of the micronutrients Fe, Mn, Cu, Zn, B, Mo and Al, showed that Fe decreased CLB severity consistently. The objective of this work was to test the effects of commercial formulations of Fe, Manny Plex Fe and Fe EDTA (Brandt Consolidated, Springfield, IL) on leaf colonization by C. kikuchii, symptom development (blight and purple leaves), and yield. Four rates of Manny Plex Fe and four rates of Fe EDTA were applied to field plots at R5 growth stage. Leaf tissue analyses for microelements and qPCR were performed. Leaf blight and purple leaf symptom severity was assessed quantitatively, and yield was measured. Results showed there was a poor relationship between leaf colonization and symptoms (neither purple nor blight). Moreover, Fe concentration in leaves did not affect biomass of C. kikuchii. Severity of purple leaf symptoms increased as Fe concentration in leaves increased, but severity decreased as Fe concentrations surpassed 230 mg/kg of dry matter. Blight symptoms were suppressed as the Fe concentration in soybean leaves increased. There was no correlation between purple leaf and blight symptoms. There was a positive relationship between leaf concentrations of Fe and yield. Negative relationships between yield and Cercospora biomass and severity of blight and purple leaf symptoms were observed.



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Committee Chair

Schneider, Raymond