Phytophthora Root Rot

Phytophthora root rot attacks alfalfa as seedlings and mature plants when the soil is saturated for several days and the soil temperature is above 60^o F.  Most modern alfalfa varieties have good resistance to this fungus disease (plant on the left).  Improving drainage is the most important management action for avoiding this important disease of Oklahoma alfalfa.  This is probably the most important disease of alfalfa in Oklahoma.