2.8.4.a What damage can heatwaves cause to vines?

Vines can withstand solar radiation and heat, which, when combined, ensure appropriate ripening of the fruit. However, high temperatures can be harmful to vines when they are sudden and/or of long duration.

A heat wave can have several consequences on vines:

• Vegetation can show signs of scorching at temperatures above 42°C. Leaves may dry out and the leaf blade may become necrotic. Berries may turn brown on the side facing the sun. Certain grape varieties are more sensitive than others, such as Viognier. Such damage is more likely to occur with stony or light-coloured soil that reflects light and retains heat. A rapid rise in temperature accentuates this phenomenon.

• High temperatures can also cause severe water stress, which is likely to lead to curling and browning of the leaves. In the most extreme cases, when there is excessive evapotranspiration, cavitations can occur, creating air spaces within the conducting vessels. This is accentuated by wind.