A Guide for Identification of Verticillium Wilt in Alfalfa

Verticillium wilt of alfalfa is distinguished by plants with one or more stems that contain leaves with pinkish-orange-brown V-shaped necrotic areas. Diseased stems remain erect and green until all leaves on the stem have lost chlorophyll. Younger leaves near the apex of the stem are partially chlorotic and twisted, forming loose spirals. Root discoloration may be present. Fields should be examined just before normal harvest. The causal organism—early grown on surface sterilized stem or petiole sections that showed disease symptoms—can be observed as verticillate (whorled) branched conidiophores with slightly enlarged, darkened bases. Most conidia produced on the conidiophores are single celled. Color plates compare verticillium wilt symptoms with other disease, Insect, and nematode damage