Fruiting in grapes

Sunburn is a kind of fruit disease caused by physiological maladjustment such as strong light, high temperature etc, which occurred in most deciduous fruit trees. So, why do grapes have sunburn symptoms?
1. Local Water Shortage:
The fruit is under the high temperature condition without shade of leaves
Leaves with high osmotic pressure compete for water from fruits with low osmotic pressure
The above reasons can be obtained that, the grapes are partially dehydrated and finally sunburned.
2. Uneven Fertilization:
Uneven fertilization ->unbalanced root nutrition of grape plants ->poor growth and tree vigor of grapes ->small and few leaves ->reduced resistance to sunlight ->fruit burns
3. Fruit Bagging Time Error:
When bagging time is too late or the temperature is too high, it will aggravate sunburn.
4. Improper Pruning of Grape plants:
Excessive pruning of branches makes the fruit pedicle unable to receive proper shade，which is prone to sunburn.

1. Too Much Nitrogen Fertilizer and Too Little Potassium Fertilizer
Grape is a grape variety that needs more potassium.
The ratio of nitrogen, phosphorus, and potassium demand of grapes should be 1:0.7~0.9.
2. Over Irrigation
Due to the excessive water and fertilizer, the vegetative growth of new shoots is too strong, and the green is too late, which is not conducive to the coloration of grapes.
3. Poor Light Transmission
As the pinching and thinning were not completed in time, the branches and leaves were too prosperous, resulting in serious shading, poor ventilation, and light transmission, so the anthocyanins were not easy to form and could not be colored.
4. Adventitious Shoots Heading Late
If the vineyard is subject to frost, the main buds in the winter buds may freeze to death, while the secondary buds may have weak growth potential and late heading due to insufficient nutrition, so the grape spikes grow slowly and it is difficult for the grapes to be colored and mature early.
5. The Measures to Promote Grape Coloring Did Not Keep Up
*Bagging time is too late
*The large dark leaves on the ear are not removed
6. Excessive Humidity
Timely moisture removal is conducive to the smooth progress of leaf photosynthesis and the improvement of leaf photosynthetic products.
8. Hyperthermia Disorder
If the temperature is too high (over 30 ℃), anthocyanins are not easy to form, leading to non-staining.
9. Pest Damage
In the process of cultivation, the leaves are damaged by diseases and insects, resulting in low photosynthetic efficiency, slow sugar content increase, and inability to color