Plant Health Initiative

Phytophthora Root and Stem Rot - Risk Assessment

Stem rot caused by Phytophthora sojae. Click on image to view a larger version. Photo credit: Anne Dorrance, Ohio State University

The disease can affect soybeans at any stage of development but is often most damaging when it occurs early in the season.

Factors that increase the risk of losses from Phytophthora diseases are:

• a field history of Phythophthora or stand establishment problems
• the number of years in soybean production - risk increases with more years in production
• heavy rains following planting; wet and warm weather conditions in the spring. Disease development is most rapid at soil temperatures above 60°F with high soil moisture.
• poorly-drained fields due to flooding, low spots, compacted soils, or a high clay content
• a susceptible soybean variety