Berry shrivel

Berry shrivel is a non-infectious physiological disorder affecting grapevines (Vitis vinifera), characterized by the sudden cessation of sugar accumulation and the shrinking of berries. Unlike fungal pathogens, this condition is not caused by viruses or bacteria, but rather by internal metabolic failures that lead to the rapid loss of berry turgor and quality.

The primary symptom is observed during the ripening stage (véraison). Berries fail to soften or color properly, becoming soft, shriveled, and maintaining a high acidity profile while lacking sweetness. This renders the crop commercially useless for both fresh consumption and winemaking, as the sugar-to-acid ratio is drastically compromised.

The biology of the disorder involves the disruption of phloem transport to the berries. Research suggests that a blockage in the rachis or the berry pedicel prevents the transport of water and nutrients, effectively starving the fruit. While the exact trigger remains a subject of study, it is widely considered to be a failure in the plant's vascular plumbing system during critical growth phases.

Environmental conditions play a significant role in the development of berry shrivel. Factors such as extreme temperature fluctuations, soil water potential imbalances, and nutrient deficiencies (specifically potassium and magnesium) increase the susceptibility of the vines. Because it is a physiological response, it does not spread through wind or insect vectors like traditional plant pathogens.

Control measures are strictly agronomic rather than chemical. Growers are advised to implement the following practices:

• Balance vine canopy to ensure optimal sugar distribution.
• Monitor and correct soil potassium levels regularly.
• Avoid excessive irrigation fluctuations during the ripening period.
• Remove affected bunches early to minimize stress on the plant's resources.