Effects of tillage, cultivar and fungicide on Phomopsis longicolla and Cercospora kukuchii in soybean

It has become a standard practice for farmers to use a no-till production system where crop residues are left on the soil surface rather than incorporated into the soil. This practice helps reduce soil erosion, conserve energy, increase soil moisture, and reduce erosion. However, many plant pathogens survive in the previous year's crop residue, increasing disease risk in reduced-tillage systems. The effect of tillage on seed borne diseases has not been objectively evaluated in side by side comparisons of till and no-till culture. We evaluated the impact of tillage and foliar fungicide on percent seed infection by Phomopsis Seed Decay (PSD) and Purple Seed Stain (PSS) over 4 years at the Milan Research and Education Center, Milan, TN. Analysis of variance indicated there was no significant difference (P ≤ 0.05) in PSD and PSS infection due to tillage. However, there was a significant interaction between fungicide and tillage where fungicide significantly reduced PSD in tilled but not in no-till plots. On the contrary, PSS increased in both tilled and no-till plots with fungicide application. These results suggest that fungicide programs under both till and no-till systems may alter the level of severity of these two seed borne diseases and may require further research to minimize the risk.