Leaf Roll (virus): Leaves roll downward and turn red between the veins progressing toward the cane tips. In California, symptoms appear in early June in non-irrigated vineyards and in August in irrigated vineyards. Vines have fewer, smaller clusters per vine with berries that are low in sugar. Red fruit varieties, such as cardinal and Mission, develop fruit lacking color, and berries of white grapes, such as Thompson seedless and Reisling, develop a yellowish-white color instead of the normal greenish-white. In general, leaf roll decreases fruit color, raises the acidity, and delays ripening. The disease is spread by propagation from infected mother vines.

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