Grape sunburn causing brown spots: what to do? Prevention methods explained

    Grape sunburn mainly occurs on the grape clusters. When the fruit is damaged, light brown patches appear, which then expand and become slightly sunken, brown, circular dry scars with indistinct edges. The damaged areas of the grapes are prone to anthracnose. It stops occurring from the coloring stage to the ripening stage. The main cause is that grapes, under high-temperature conditions lacking leaf shade, lose water locally and are scorched, or that leaves with high osmotic pressure compete for water from grape berries with low osmotic pressure.

Grape sunburn

    1. Choice of trellis system. Trellis cultivation should be chosen. After the grapes are planted, fertilizer and water inputs should be increased to promote rapid growth, so that in the second year the grapes form a trellis tree shape, keeping the grape clusters beneath the trellis surface and avoiding direct sunlight on the grapes.

    2. Watering. From fruit set until early July, the berries are tender and have poor resistance to sunburn. At this time, with little rain, high temperatures and dry air, sunburn is most likely to occur; in mild cases some berries are scorched, and in severe cases the rachis dies and the entire cluster dries up. According to weather conditions, water appropriately to lower the temperature in the vineyard and reduce sunburn damage.

    3. Flower and fruit thinning, and bagging the clusters. Determine the yield according to soil fertility and vine age. Before full bloom, when the flower clusters separate, thin the flowers in time. Remove excess berries; after thinning, spray a fungicide once, then bag. Choose waterproof, white paper bags with ventilation holes at the bottom. White paper bags absorb heat poorly and are safe to use. When bagging, avoid the midday high temperatures and periods with dew.

    4. Strengthen fertilizer and water management to enhance the grapes' resistance to sunburn. Grapes like fertilizer and water; organic fertilizer should be applied more, watering should be done at the right time, and pest and disease control should be carried out well, so that the vines are robust and their disease resistance is enhanced.