Symptoms first appear on scattered plants as yellow, twisted or drooping leaves on one or more stems. A V-shaped, yellow blotch on the leaflet tip is often an early sign of infection. Eventually leaves on infected stems turn from green to yellow to a bleached tan colour. Infected plants become stunted, and are very susceptible to winter kill. The key plant symptom is that stems remain green and upright even though leaves are wilting or near death.
Stems tend to wilt.
Look for drooping and wilting of the whole plant and bleaching of leaves. Sometimes just the top of the plant is affected. Verticillium wilt can be introduced into a field by contaminated farm machinery, contaminated seed, or by air-borne spores from neighbouring, infested fields. Once the disease is present it is easily spread while cutting the crop. Other methods of spread include irrigation run-off from infested fields, movement of contaminated hay, and in manure from animals fed contaminated hay.