by: Anne Dorrence, OSU Extension
Only Susceptible Varieties are Prone to Diseases and May Require a Fungicide Application.
From the scouting reports from the county educators and crop consultants – most of the soybeans in the state are very healthy with no disease symptoms. However, as the news reports have indicated, there are a few varieties in a few locations that have higher incidence of frogeye leaf spot than we are accustomed to seeing at this growth stage – mid R2 – flowering in Ohio. Most of the reports to date are along and south of route 70, which based on the past 12 years is where frogeye is the most common. When this disease occurs this early in the season, where it can be readily observed, this is a big problem and should be addressed right away with a fungicide soon and a second application at 14-21 days later depending on if disease continues to develop and if environmental conditions (cool nights, fogs, heavy dews, rains) continue. Table 1. Lists the fungicides that have very good activity towards frogeye leaf spot based on University trials around the country (thank you land grant university soybean pathologists in NCERA-137). Note that on this list there are no solo strobilurin fungicides, as we have detected strains of the fungus, Cercospora sojina, that are resistant to this class of fungicides in the state.