The cool temperatures this spring have slowed alfalfa growth and slow alfalfa growth can delay the buildup of foliar diseases. We checked alfalfa fields in Ames this weekend and observed foliar diseases on the bottom leaves of plants in some fields. The levels of these diseases were not high, but they may increase before the first cutting. Cool temperatures and frequent spring rains are favorable for the development of foliar diseases in Iowa.
Iowa State University
Yang, X. B. and Munkvold, Gary P., "Spring alfalfa leaf diseases in 2001" (2002). Integrated Crop Management News. 1850.