Soybean Diseases
By Laura Sweets

Soybean Seedling Blights and Root Rots
This year many soybean plants seem to be off to a slow start. Dry soils, cold soils, sudden changes in weather conditions have slowed germination and emergence in some fields. When soybean germination and emergence is delayed soil pathogens such as Pythium, Rhizoctonia, Fusarium and/or Phytophthora have a greater opportunity to attack slowly growing plants. We are receiving questions related to poor emergence, uneven emergence, stunted plants and plants that are yellowing or even dying. On plants that are stunted, showing yellowing or scorching of lower leaflets and discoloration of root systems, Rhizoctonia and Fusarium appear to be the pathogens associated with these symptoms. See the May 27 issue of the Integrated Pest and Crop Management Newsletter for descriptions of the early season soybean diseases.

Soybean Foliage Diseases
So far, Septoria brown spot is the primary foliage disease showing up on soybean leaves. Symptoms seem to be most prevalent on the lowest leaves and spots may be very small. The typical Septoria brown spot lesions with fungal fruiting bodies evident in the center of the lesion aren’t showing up yet. Again with the current forecast of hot, dry weather for much of the state, Septoria shouldn’t be spreading very much. The disease is more likely to move under conditions of frequent rains, heavy dews and overcast days.

We have not yet received any samples with bacterial blight or bacterial pustule. Although these diseases might show up after the heavy storms that moved through central Missouri the weekend of June 10-11.

Laura Sweets
573-884-7307