Iowa State University researchers recently published their annual fungicide trial data for soybeans in 2019, revealing a continued decline in efficiency among the quinone outside inhibitors (QoI) class of fungicides in preventing foliar diseases in soybeans.
These research results confirm Iowa State findings that foliar fungal disease continues to develop resistance to quinone outside inhibitors class of fungicides.
- Use a product with multiple modes of action.
- Selection of disease-resistant cultivars.
The charts below showcase results from the ISU Research Farms.
Fungicides reliant solely on QoIs had decreased efficacy against both frogeye leafspot and Septoria brown leaf spot, which are the main foliar diseases of concern in Iowa, and did not provide profitable yield increases. Therefore, researchers conclude that unnecessary use of foliar fungicides should be minimized and an integrated method of disease management that does not depend solely on foliar fungicides should be employed. If a fungicide application is deemed necessary, consult a current efficacy chart like the one produced by the Crop Protection Network to select a fungicide that will control the disease of concern.