The precipitation that occurs in connection with thunderstorms in the form of ice balls or lumps with a diameter of five to 50 millimetres (rarely even larger) is produced in rapidly rising, moist air currents. Depending on their size, the hailstones can perforate or completely destroy the leaves and damage the shoot tips, which in extreme cases can lead to complete defoliation. If large parts of the foliage and thus the assimilation area are affected, the growth and development of the vine is impaired, which can also have an impact on the next harvest. One possible consequence of defoliation is grape wilt caused by sunburn, for example.
At the time of flowering, hail is particularly feared in vineyards and can lead to coulure inadequate fertilisation. In extreme cases, hail can completely destroy entire harvests in a short space of time. During the ripening period, even light hail can damage the berries, and red wine grapes are particularly susceptible. This damage favours infestation by bacteria, insect pests and fungi. Under certain weather conditions, white rot caused by a fungus (hail disease) can occur. See also other negative weather influences under drought (dryness), frost and wind, as well as the general topic of climate and meteorology.
Hailstones: Image by Hilde Stockmann on Pixabay
Hail damage: SYNGENTA - Dr Bernd Loskill, Syngenta Agro
For my many years of work as an editor with a wine and culinary focus, I always like to inform myself about special questions at Wine lexicon. Spontaneous reading and following links often leads to exciting discoveries in the wide world of wine.
Dr. Christa Hanten
Fachjournalistin, Lektorin und Verkosterin, Wien