Minimising bunch stem necrosis in wine grapes
Bunch stem necrosis (water berry) in grapes affects fruit set and fruit ripening. It can occur around the bloom, in which case it is called early bunch stem necrosis, at veraison or later. The occurrence of it is associated with weather conditions and crop nutrition.
During bloom, the symptoms of bunch stem necrosis begins as the pedicle elongates. It can become necrotic, resulting in the dropping of the flower buds. Later, entire sections of the inflorescence can shrivel and die, and may or may not drop off. The symptoms appear as necrotic patches on the rachis or pedicle. As a result, the supply of water and nutrients are limited, leading to wine grape berries with less sugar, remain sour and eventually shrivel.
Crop Nutrition and bunch stem Necrosis in Wine Grape
Magnesium
Bunch stem necrosis is often associated with a magnesium deficiency and the imbalance of magnesium and nitrogen. Research suggests that low levels of sugars in storage organs and fruit lead to nitrate accumulation, particularly during cold weather during maturation. Two to three foliar applications of magnesium starting just before veraison minimise the problem.
Recommended Yara fertilisers for grapevines
How nutrient management affects wine grape
Influencing grapevine yield
High grapevine yields are obtained on the most freely drained soils where water is not limiting. Vines will grow across a wide range of soil pHs, but extremes will render many nutrients unavailable and thereby restrict yield.
Increasing grape berry set and weight
Nitrogen and phosphorus are significant in increasing wine grape berry set and weight.
Improving grape quality
The aim of any grower is a high yielding, top quality wine grape that satisfies the wine-maker. Both yield and quality are strongly influenced by nutrition.
Influencing grape and wine pH
Strong vine canopies can lead to excessive nitrogen and potassium uptake, which increases grape and wine pH.
Grape nutrient deficiencies
Identify and diagnose if your grapes are suffering from nutrient deficiencies and learn more about the symptoms and causes and how to control or correct the deficiency
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