What to Do About Grape Berry Cracking in Autumn? These Control Methods Are Very Practical
Grape berry cracking mainly occurs in the near-ripening stage of the berries. The symptoms are cracked skin, loss of commercial value, and because the juice leaks out, it easily causes the spread of pests and diseases, further increasing losses. So what should be done about grape berry cracking in autumn? Perhaps the methods below can help you!
I. Causes of grape berry cracking
1. Variety characteristics
Varieties with tightly packed berries and thin, brittle skins are prone to cracking, such as Zana, Xiangfei, Zhengzhou Zaoyu, Victoria, and Kyoho.
2. Sharp changes in soil moisture
When grapes are near ripening, severe changes in soil moisture and air humidity may cause berry cracking. If there is drought in the early stage, the grape's flesh cells remain in a thirsty state. If heavy rain falls repeatedly during the near-ripening stage, soil moisture increases sharply, the root system absorbs a large amount of water, and a large amount of water is transported to the berries through the pedicel, causing the physiological activity and division activity of the flesh cells around the pedicel to accelerate, while the flesh cells near the skin move slowly. The swelling pressure of the berries gradually increases, ultimately causing berry cracking. Therefore, in orchards with poor irrigation conditions, low-lying terrain, heavy clay soil, and poor drainage, berry cracking occurs severely.
3. Berry compression
Because fruit set is good, large clusters are not properly thinned, and too many berries are left, the berries are too tightly packed. During fruit enlargement, the berries squeeze and deform each other, leading to cracking.
4. Unreasonable summer pruning methods
When many grape growers prune in summer (pinching), in order to save time and effort, they break off shoots as soon as they see them. Some even set a height and carry out “flat-top” summer pruning, which is wrong. This not only reduces the number of effective functional leaves and weakens transpiration, but also affects the orderly growth of new shoots, weakens the new shoots' ability to regulate fertilizer and water, and aggravates cracking.
5. Berry disease or improper pesticide spraying
When berries suffer from diseases such as powdery mildew and downy mildew, the skin is easily damaged. If these are not controlled in time, when the berries enlarge, the flesh presses against the skin, which cannot withstand the pressure and cracks.
If pesticides such as tegdyn or other agricultural chemicals for controlling grape diseases are sprayed continuously, transpiration will be reduced, and a large amount of water in the tree will flow to the berries, increasing berry turgor pressure and making cracking most likely.
Some people use ethephon or abscisic acid for ripening. If the spraying concentration is too high or it is applied too early, it often also leads to berry cracking.
6. Improper fertilization
Improper fertilization leads to a deficiency of calcium, boron, potassium, and other elements in the soil, which can cause berry cracking. If the berries already have a tendency to crack, the lack of nutrient elements will worsen the cracking.
II. Methods for managing grape berry cracking
1. Choose crack-resistant varieties
Choose crack-resistant varieties to fundamentally reduce the occurrence of cracking, such as Red Globe, Summer Black, Beauty Finger, and Autumn Black, which are not prone to cracking.
2. Maintain balanced soil moisture
Regulate soil moisture well, so that there is no water shortage in drought and no water accumulation in waterlogging. Reduce the difference between dry and wet soil. When the soil is dry in the later stage of fruit growth, irrigate the grape roots in time, and prevent flood irrigation. After the fruit begins to color, in case of drought, water once every 7~10 days, and keep the soil moisture content at 60%~70%, which can effectively prevent berry cracking.
3. Reasonable fertilization and pesticide application
Apply organic fertilizer heavily, fertilize according to different soil types, apply nitrogen, phosphorus, and potassium fertilizers reasonably, do not apply nitrogen fertilizer alone, and be sure to spray nutrient elements such as calcium, boron, and potassium. Foliar spraying takes effect quickly and works well.
At the early stage of disease occurrence, begin using agents for prevention. When diseased berries are found, first cut off the diseased berries, then spray chemicals for control. During a one-year growth period, tegdyn must not be used more than 3 times. The suitable concentration for ethephon ripening is 500 mg/kg, and for abscisic acid it is 100 mg/kg, and it must be used when 5%~10% of the berries have colored, to prevent berry cracking.
In addition to the above measures, during the second fruit enlargement stage, spray the fruit clusters once with 500 mg/kg rare earth every 7~10 days, for 2 consecutive times. When preparing, first use vinegar to adjust the water into a slightly acidic solution (pH 5~6), then add the rare earth, and spray on a cool sunny day to prevent berry cracking.
4. Thin fruit and thin branch clusters
Keep the tree body at a stable and suitable fruit-setting amount, so as to ensure that the fruit clusters obtain sufficient water and nutrients. Generally, 2500~3000 kg of fruit per mu is appropriate.
Keep the shoot spacing at about 10 cm, the leaf-to-fruit ratio at 15~20:1, leave 2 clusters of fruit on strong shoots, 1 cluster on moderate shoots, and no fruit clusters on weak shoots. Remove secondary clusters in time and pinch the cluster tips so that the fruit clusters are moderate in size.