Production of specialty soybeans, such as tofu soybeans, brings new opportunities for soybean growers. As more and more growers plant specialty soybeans, which are not commonly bred for disease resistance, we have received an increased number of questions on disease management. Stand reduction is often caused by seedling diseases, such as Phytophthora damping-off, which can be a problem on soybeans that do not have Phytophthora resistance. This type of problem is easy to fix either by preparing a better seed bed or by planting specialty beans in a field with a low infestation. Conventional tillage also can reduce seedling disease problems if no-till fields are involved.
Seed treatment can be another effective fix.
Some seedborne diseases cause discoloration in harvested seeds, which may affect seed quality of specialty beans. One type of discoloration is purple seed stain caused by Cercospora kikuchii . Infected seeds have seed coats with purple blotches. The stage of this disease in the summer is called Cercospora leaf spot, a fungal disease that has recently increased in importance. The fungus survives in infected seeds or soybean debris and during the growing season infects soybean seeds at pod set.