The persimmon tree can experience fruit drop due to two main causes: physiological fruit drop and fruit drop caused by pests. Both issues can lead to significant economic losses, especially in certain years. Understanding the reasons behind these drops is essential for effective management and prevention.
**Causes of Physiological Fruit Drop**
1. **Nutritional Imbalance**: When new shoots are actively growing, they consume a lot of nutrients, which can lead to fruit drop. If flower buds don't develop properly, it can also result in early fruit loss.
2. **Poor Pollination**: Some persimmon varieties, like the large grinding disc, don’t require pollination. However, most sweet Japanese varieties need pollination trees. Without proper pollination, especially during rainy seasons, fruits may not develop properly and fall prematurely.
3. **Unbalanced Tree Structure**: Trees that are too tall or have dense branches may suffer from poor air circulation and light penetration, leading to weak growth and increased fruit drop.
4. **Inadequate Water and Fertilizer**: Prolonged drought or poor soil quality can reduce nutrient uptake, causing more fruit to drop. Excessive moisture can also hinder root absorption, even with added fertilizers, leading to nutrient deficiencies and fruit loss.
5. **Impact of Rainfall**: Heavy rainfall reduces sunlight, weakening photosynthesis and limiting nutrient availability to developing fruits, which can trigger premature dropping.
**Fruit Drop Caused by Pests and Diseases**
1. **Persimmon Worms**: These pests damage fruits before and after harvest, causing them to become soft and fall off, reducing yield.
2. **Persimmon Tree Beetles (Tree Shrews)**: These insects cause serious fruit drop and harm the overall health of the tree.
3. **Anthrax Disease**: This disease typically occurs in September and leads to widespread fruit drop. Preventive measures include applying lime sulfur before bud break and using Bordeaux mixture in mid-June and mid-August.
**Prevention and Control Measures**
1. **Improve Fertilization and Irrigation**: Ensuring the tree receives adequate nutrients and water helps maintain its health and supports better fruit development.
2. **Pruning**: Regular pruning, especially in summer, helps improve air circulation and light exposure, reducing fruit drop and promoting healthy growth.
3. **Pollination Management**: For varieties requiring cross-pollination, planting compatible male trees and using artificial pollination can significantly reduce fruit drop.
4. **Girdling**: Girdling the trunk or main branches can encourage earlier flowering and reduce fruit drop. It should be done at half the blossom period, with a width of no more than 1.5 cm to avoid damaging the tree.
5. **Pest and Disease Control**: Applying lime sulfur before bud break, using Bordeaux mixture, removing infected fruits, and spraying insecticides like Lethbone and Avermectin can help control pests effectively.
6. **Use of Growth Regulators**: Spraying 500 ppm gibberellin or adding 1% urea can help prevent fruit drop and improve fruit set.
By implementing these strategies, growers can minimize fruit drop and ensure better yields and quality of persimmons.
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