DISEASES OF ALFALFA - DOWNY MILDEW

In addition to spotting diseases, there are several diseases, the major symptom of which is a yellowing of leaf tissue. Downy mildew, caused by Peronospora trifoliorum, is one such disease. After infection by the fungus, affected leaves begin to exhibit blotchy, yellow areas (see leaf on left above). After periods of high humidity, downy, gray-white hyphae and reproductive structures of the pathogen are visible on the underside of symptomatic leaves (see arrows).