Use of foliar fungicides in soybeans has been shown to improve crop health in soybean varieties susceptible to various fungal diseases. This improvement in crop health can result in a 2.6 bushel per acre increase in yield. When insecticide was included in treatment, response increased to 5.3 bushels. (Pioneer) Many factors must be considered before choosing to apply a foliar fungicide. These include current and forecasted humidity levels, amount of rainfall, and type and amount of residue from the previous crop. Additionally, type of disease present is important in soybeans. Diseases originating in the root system will not be controlled with fungicides. Neither will diseases stemming from bacterial or viral diseases such as bacterial blight or soybean vein necrosis.

Fungicides will be effective on fungal diseases for 14-21 days after application. Applications are usually timed to ensure this timeframe for protection falls between pod set and maturity to protect the reproductive stages of the growing season. Generally, we shoot for applications around R3, which is the start of pod development. Some research from the University of Illinois suggests that a single application at R3 is just as effective as two applications at R3 and R5. Other research from BASF suggests that two fungicide applications are beneficial. We wanted to discover what the average response in our geography is. Over the past 4 years, we have tested fungicide trials across the county to see what kind of response we can see in a typical year.