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Disease cycle, symptoms and management practices for phytophthora root rot are discussed in this NebGuide.
Phytophthora root rot (PRR) is a major cause of seedling death in newly established alfalfa, and causes a progressive decline of established stands in Nebraska. This disease is caused by the fungus Phytophthora megasperma f. sp. medicaginis and occurs in most of the alfalfa producing areas in North America.
The Phytophthora that infects alfalfa is different from the Phytophthora that causes root rot in soybeans. Growers sometimes think the two diseases are the same for the respective crops, but they are two different diseases with the common name of phytophthora root.