What causes grape fruit cracking?
Let me tell you about the maintenance of grape trees, what causes grape fruit cracking, please see the detailed introduction below.
Grape fruit cracking is a common physiological disease of grapes, which often occurs near maturity. The cracking usually happens near the fruit stem, with circular cracks extending from the stem, and also longitudinal cracks extending from the fruit. After cracking, the temperature and juice factors lead to decay and leakage. This attracts flies and other insects to eat the fruit and juice, thereby spreading pathogens throughout the orchard.
I. Reasons for grape fruit cracking
1. Variety influence: Some varieties have thin and brittle skin, which is prone to cracking. For example, Zana and Rizamat, etc., these varieties are more likely to crack.
2. Soil moisture influence: Drought in the early growth stage of grape fruits (spring drought), followed by heavy rain or excessive irrigation during the second fruit expansion period to maturity (rainy season), causes a sudden increase in soil moisture. The roots absorb a large amount of water, increasing the pressure on the fruit expansion and leading to cracking.
3. Fruit setting influence: Natural fruit setting during the flowering period is relatively dense, causing excessive pressure on the fruit cluster during the second expansion, leading to cracking due to mutual compression of the fruit.
4. Influence of grape vines: Excessive reservation of branches during the green shoot training period leads to too many leaves, dense vine growth on the trellis, poor ventilation, and poor light penetration. Excessive reservation of fruit clusters and too few leaves during the green shoot training period leads to an imbalance in leaf and fruit metabolism, resulting in fruit cracking.
5. Pesticide influence: For example, continuous spraying of fungicides like Captan can reduce transpiration, causing a large amount of water to flow into the fruit, leading to excessive pressure on fruit expansion and cracking.
6. Temperature influence: High temperatures during the young fruit stage, especially in greenhouse conditions, can lead to cracking.
7. Artificial maturation influence: High concentration or early application of maturation chemicals can cause cracking.
II. Methods to prevent grape fruit cracking
1. Variety selection: Careful variety selection is essential at the beginning of planting. With experience, you can try planting varieties that are prone to cracking.
2. Preventing soil moisture imbalance: Maintain relatively stable soil moisture. Irrigate in time during dry periods to supplement soil moisture, and drain excess water during heavy rain. During the second expansion period to maturity, pay attention to less frequent but multiple watering to avoid sudden increases or decreases in soil moisture. During the rainy season, using plastic mulch on the ground can prevent the impact of rain on the soil. Planters with conditions (especially in southern regions) can use rain-shelter cultivation to effectively prevent the impact of rain on soil moisture.
3. Management requirements during flowering and post-flowering: For varieties with dense fruit setting, you can change pre-flowering pruning to post-flowering pruning to promote natural fruit drop, or thin the fruit after flowering to achieve moderate fruit density and prevent cracking.
4. Adjusting the ratio of leaves, branches, and fruit clusters during the green shoot training period through thinning branches and clusters. Generally, maintain a leaf-fruit ratio of 10-20:1 (the ratio varies by variety), with strong branches having two fruit clusters, moderate branches one fruit cluster, and weak branches having no fruit. Timely remove auxiliary spikes and pinch off the fruit tips to keep the fruit cluster size moderate.
5. Pesticide use: Alternate between different pesticide formulations and pay attention to avoid phytotoxicity.
6. For greenhouse cultivation of grapes, the temperature during the young fruit stage should not exceed 26 degrees Celsius.
7. Strictly follow the proportions when using maturation chemicals, avoid exceeding the concentration, and choose to spray in the morning around 9 am. Do not expose the sprayed fruit to rain within 8 hours after application. Appropriate calcium fertilization can be applied in the early and middle stages of fruit growth to prevent cracking.
The above information introduces the reasons for grape fruit cracking and methods for prevention, which you can use as a reference.