In Iowa, severe SDS is more likely to be found in early planted soybean fields than in late-planted fields. This spring, excessive soil moisture together with cool soil temperatures would mean higher disease risk to early planted soybean fields. If your fields showed SDS in the past, consider planting later until the soil warms up to reduce disease risk. Planting date also indirectly affects occurrence of white mold, pod and stem blight, and brown stem rot. Soybean has certain growth stages during which it is susceptible to white mold and pod and stem blight.
Soybean reaches the susceptible stages in the summer according to the planting time.
For example, with white mold, more disease was observed in late-planted soybean in 1996 because the cool and wet weather came late in the season. However, we cannot manipulate planting to control these diseases because we cannot predict weather that far in advance. The table below summarizes how planting date affects major Iowa soybean diseases. It also includes seedling diseases. Keep in mind that if your fields had no disease problems in the past, diseases should not be a factor in your planting date decision because Iowa has a short planting season for maximum yield.