Master of Science (MS)


Plant Pathology and Crop Physiology

Document Type



To study the effect of Silicon (Si) with and without a fungicide on anthracnose development of sorghum, several experiments were conducted in the greenhouse and field. In the initial study, different Si rates [0 (control), 0 (lime control), 200, 400, 600, 800 kg Si/ha] were used in a low-Si Alfisol to determine if inoculum densities were affected by Si levels. No differences were observed between inoculum densities of 1*105 and 1*106 conidia/ml in affecting anthracnose development in the greenhouse. Anthracnose severity was found to be lowest in plants treated with 800 kg Si/ha, regardless of inoculum density. In another study, the effect of Si on moderately susceptible (Pioneer 84G62) and moderately resistant (Pioneer 84P80) hybrids was also examined with lower inoculum concentration under greenhouse conditions. Fungicide (Pyraclostrobin) was also included to suppress the anthracnose development. Silicon had a significant effect on plant Si concentration and anthracnose development. Anthracnose severity was reduced as plant and soil Si levels increased. The highest Si application rate (800 kg Si/ha) reduced Final Disease Severity (FDS) and Area Under Anthracnose Progress Curve (AUAPC) by 18 and 36% as compared to the control for the first greenhouse experiment (p<0.05). Likewise, it reduced FDS and AUAPC of the 2nd greenhouse experiment by 76 and 67%, respectively (p<0.001). Pyraclostrobin effectively reduced AUAPC by 50 and 36%, respectively, for the two greenhouse experiments. Similar Si + pyraclostrobin experiments were conducted under field conditions at Dean Lee (Inceptisols) and Winnsboro (Alfisols), Louisiana with higher soil Si levels (120 µg/g and 40 µg/g respectively). Even though soil Si increased with higher Si rates for both fields, no significant increase in Si accumulation in sorghum leaves or grains was observed. At Dean Lee, pyraclostrobin reduced AUAPC by 44 and 39% and FDS by 50 and 48%; respectively, for Pioneer 84G62 and Pioneer 84P80 (p<0.001). However, pyraclostrobin had no effect in reducing anthracnose at Winnsboro. Yield was higher for Pioneer 84G62 than Pioneer 84P80 at Dean Lee. Silicon had a greater impact in suppressing anthracnose development on low-Si soils under greenhouse conditions than high-Si soils of the field.



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Committee Chair

Hollier, Clayton A.