P-147 - Effect of planting date on red crown rot of soybean

Red crown rot (RCR), caused by Calonectria ilicicola, has historically been known as a disease of the southern United States. However, it has become an emerging disease in the midwestern states, when it was first confirmed in Illinois in 2018. Since then, it has been confirmed in surrounding states, such as Kentucky in 2021. Current RCR management recommendations are limited. One of the historical recommendations has been to delay soybean planting. However, in Kentucky, RCR has been observed to be more severe in fields that have been planted later in the growing season. Field trials were conducted at the University of Illinois Orr Agricultural Research & Demonstration Center from 2022 to 2024 to determine the effect of planting date and seed treatment on RCR. Treatments included three planting dates in April, May and June in fields that had been infested with C. ilicicola and seeds either treated or non-treated with fluopyram. When evaluating plots with non-treated seed, the  the greatest disease severity index (DSI) values were observed in June plantings in 2022 and 2024. In general, low DSI was observed across the trial in 2023. The effect of fluopyram seed treatment was variable across years and planting dates, where in some cases, reductions in DSI was observed, but in some other cases, DSI increases were observed with fluopyram. More research is needed to better understand the effect of fluopyram on RCR across different planting dates or soil temperatures.