Heat Wave. Although grapevines thrive in warm areas, a prolonged heat wave coupled with scarce water stresses the plant, causing the foliage to shrivel and droop. If high temperatures continue and irrigation or rainfall water remain insufficient, the leaves turn brown and the canes shrivel and dry.

Why are my grape leaves turning yellow and brown?

Iron deficiency is the most common culprit that causes yellowing — leaf tissues turn yellow, with the only the veins remaining green. It is often the result of high soil pH in wet conditions. … Potassium deficient grapevines resemble those that are iron deficient, except that the leaf will eventually dry out and die.

What's wrong with my grape leaves?

Black spot, powdery mildew, and anthracnose are just a few of the common fungal diseases. They most commonly affect the foliage with spotting or a coating, but may occasionally threaten twigs and terminal tissues. The fungus reduces the plant’s effectiveness at gathering solar energy and can cause leaf loss.