Assessing Foliar Fungicides for Soybean Disease Management and Yield in Indiana

Foliar diseases can significantly impact soybeans in Indiana, and fungicides can be an effective management tool to protect yield against disease. Fourteen foliar fungicide products were evaluated for efficacy on soybean foliar diseases and yield in 10 field trials from 2019 to 2021 in Indiana. Fungicides were applied at their recommended rates in a single application at the beginning pod (R3) growth stage. Cercospora leaf blight (Cercospora spp.), brown spot (Septoria glycines Hemmi), and frogeye leaf spot (Cercospora sojina Hara) were the most prominent foliar diseases observed in the trials. Under low to moderate Cercospora leaf blight disease pressure, there were no significant differences between foliar fungicides and the nontreated control averaged across all site-years. In contrast, all foliar fungicides significantly suppressed brown spot from 69 to 92% relative to the nontreated control. Only bixafen + flutriafol and azoxystrobin + pydiflumetofen + propiconazole significantly suppressed frogeye leaf spot severity over the nontreated control. Foliar fungicide applications did not significantly increase yield over the nontreated control across all site-years. Therefore, under low to moderate foliar disease risk, fungicide applications may not be warranted in Indiana. Growers should continue to scout soybean fields prior to the beginning pod (R3) growth stage, then make an informed, sustainable decision to use a fungicide for disease management.