This disease is usually seen during the cooler periods of the year. Crop rotation, with two to three years away from alfalfa, aids in control. Verticillium wilt may be spread from field to field with infested seed and in manure from animals fed infested hay. This soilborne disease usually does not become a problem until the third production year. It can be recognized on scattered plants that become yellow and stunted, then gradually die, leaving a thin, unproductive stand.
Control is mainly through use of disease-free seed, resistant varieties, and crop rotation.
There are several foliage diseases of alfalfa. Any of these may cause considerable loss of leaves during periods of prolonged wet or humid weather. Little can be done about these diseases in the year that they occur. Proper crop rotation will help control these diseases in following years. Consult The OSU Horticulture and Crop Science Series 195, Ohio Forage Performance Trials for a listing of alfalfa varieties and their level of resistance to various diseases.