Phytophthora Root Rot in Alfalfa

The center plot  is root rot susceptible, others are resistant or moderately resistant.  Phytophthora root rot occurs in  alfalfa when the soil temperature is higher than 60^oF (16^oC) and the soil is saturated for several days or weeks and the plants are susceptible.  The above ground symptoms include stunted growth and yellowing (middle right)