The Occurrence Regularity of Grape Sunscald Disease
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The Occurrence Regularity of Grape Sunscald Disease
A non-infectious physiological disease known as sunburn commonly occurs on fruit trees in northern China. For grapes, this disease is very serious, and once infected, neither field cultivation nor facility cultivation can be exempted. If the disease is severe, there will be no harvest, causing significant economic losses to fruit farmers. How to effectively avoid it? Let's find out.
Sunburn Symptoms
Grape sunburn mainly affects the plant's fruits, especially young fruits. The damaged fruits first form irregular, near-circular brown spots at the damaged site. As the condition worsens, the damaged area will gradually sink and dry, affecting the appearance quality of the fruit and significantly reducing its commercial value. Since this disease is mainly caused by high temperatures and strong light, the most severely affected areas are fruits exposed to plenty of sunlight.
The Occurrence Regularity of Sunburn
The occurrence of grape sunburn is not only related to climate and environmental conditions but also influenced by tree strength, load size, and leaf quality. For example, increased evaporation caused by high temperatures and low humidity can lead to severe water loss, resulting in the occurrence of this disease; in addition, unreasonable growth such as overly weak or strong tree vigor, excessive plant load, poor ventilation and light penetration, unreasonable fertilization structure, and thinning fruits under direct sunlight at noon. These factors can directly or indirectly cause or exacerbate sunburn, with the most important being climatic factors such as high temperatures, low humidity, and direct sunlight, which should be considered when formulating control measures.
Prevention and Control Measures for Grape Sunburn
Based on the analysis of the occurrence regularity of grape sunburn and related production practices, the following methods can be adopted to control grape sunburn.
1. Carry out adaptive control work according to climatic and environmental conditions
Through the "occurrence regularity" section, we find that climatic and environmental conditions play a vital role in the occurrence of grape sunburn, so this must be prioritized in control work, as follows:
(1) Greenhouse grapes: The temperature and humidity inside the greenhouse should be controlled appropriately through operations, with the temperature at 22-25°C during the day and 9-12°C at night; humidity is generally regulated through frequent watering and a small amount of water.
(2) Field grapes: Grapes planted in this way are most susceptible to direct sunlight, so when establishing an orchard, consider a small shed cultivation method. This cultivation method has a significant effect on preventing sunburn. Since vertical frame cultivation (note: both cultivation methods have their pros and cons, so the choice must be based on local conditions) can also use double-layer paper bags to prevent the occurrence of sunburn. We must pay attention to choosing paper bags and use white paper bags cautiously.
2. Adjust according to tree shape and condition
Although tree condition is not the main cause of grape sunburn, weak trees greatly increase the incidence of this disease, so corresponding management work must be done in production to cultivate moderately strong trees. In addition, for orchards with severe sunburn, targeted pruning should be carried out to ensure that fruit branches are not affected by direct sunlight. Specifically, during summer pruning, more leaves can be left near the fruiting zone, and the fruiting zone can be flipped to a shady place in a timely manner. In areas without fruiting zones, some leaves should be removed to reduce the number of young leaves and avoid excessive leaf cover competing with the fruit for water.
3. Reasonably match according to fertilizer types
Currently, the most widely used fertilization method in agriculture is soil testing and formula fertilization. This method mainly selects combined fertilization based on soil fertility. This method also has a certain effect on preventing grape sunburn. If this fertilization method is not adopted, the amount of nitrogen fertilizer should be appropriately reduced, and the application of phosphorus, potassium, calcium, and other fertilizers should be increased, especially before the onset of the disease, which is more effective.
The specific reasons are as follows: The more nitrogen fertilizer applied, the more the tree will grow in vain, consuming a large amount of nutrients and water. At this time, if the weather is hot, the berries will lose a lot of water first, and then sunburn will occur; applying phosphorus, potassium, and calcium fertilizers can significantly promote root growth, thereby enhancing plant drought resistance and reducing the probability of sunburn to some extent.
4. Learn more from the thinning period of fruits
Grape sunburn often occurs during the thinning period, so it is essential to prevent sunburn caused by improper operations during this agricultural activity. According to the production experience of fruit farmers, grape thinning should avoid direct sunlight at noon, mainly between 10 am and 3 pm, and protective measures should be taken to prevent the fruit powder on the grape surface from falling off, increasing the incidence rate.
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