Leafroll virus

Distribution: This disease is found in most grape-growing areas.

Symptoms are most obvious in fall. Infected vines are slightly smaller than healthy vines. Leaves become yellow or reddish purple as the season progresses; the main veins remain green. By late summer, the leaves start rolling downward, beginning at the base of the shoot. At harvest, fruit clusters are small, poorly colored and low in sugar. The disease does not kill the vine but will remain chronic. Not all infected vines show symptoms. The leafroll virus spreads primarily via infected nursery stock and the grape mealybug. Within-field spread by mealybug is very slow.