B-791R

 Phytophthora root rot (PRR) is a major alfalfa disease throughout North America. PRR is common in irrigated alfalfa in Wyoming and is particularly severe in the Big Horn and Wind River basins. The disease is caused by the soilborne fungus Phytophthora megasperma f. sp. Medicaginis (P. megasperma).

 Biology and management of Phytophthora root rot of alfalfa discusses the symptoms, cycles, and management of the disease. According to the authors, “The presence of PRR in established stands results in loss of hay yield, loss of hay quality due to weed invasion, and shortened stand life.”

The four-page bulletin explains that planting varieties with resistance to the disease are recommended in fields with a history of PRR. This increases protection not only during establishment but through the life of the alfalfa stand.