Symptoms of white mold as seen in 2018 in a field in Centre County. Image credit: P. Esker
While not as widespread as in 2016, white mold of soybean is causing problems in several fields and has been seen in fields in the northern parts of Pennsylvania. We have been receiving questions about the potential impact to reduce yield and if there are methods to estimate the potential losses. As we wrote in our 2017 article, "What to Do if I Have White Mold in Soybean?," at the R7 growth stage (beginning maturity) we can quantify the incidence of white mold in the field by taking observations from different points in the field (for example, visit 100 random plants in a field) and count the number of plants that have symptoms of the disease. Yield loss can be estimated as follows: for every 10 out of 100 plants affected by white mold at R7, yield can be reduced by approximately two to five bushels per acre. This information will be very important to start to consider management options for 2018.