What causes persimmon trees to drop their fruit?
Persimmon is a fruit widely loved by people, able to promote fluid production and clear heat, and to strengthen the spleen and benefit the stomach. But during the growth process, persimmons may show the phenomenon of flower and fruit drop. Why do persimmon trees drop their fruit? Actually there are mainly two reasons: one is physiological fruit drop caused by the persimmon tree's own physiological disorder, and the other is fruit drop caused by pests and diseases such as anthracnose or persimmon stem borer.
1. Physiological fruit drop of persimmon trees
The degree of physiological fruit drop in persimmon trees varies greatly among cultivars. For example, the main cultivar in the Taihang Mountain area of our province, Da Mopan persimmon, drops fruit relatively lightly, generally not exceeding 10%, and is not easy to notice, while the Dahongpao cultivar, after entering the full fruiting stage, drops fruit severely, with a fruit drop rate of up to 2/3 at most.
The degree of physiological fruit drop is related to the fruiting position. On the same tree, fruit drop is less on the outer periphery and upper part of the canopy, and greater on the lower part and inner canopy, which is related to the different degrees of light exposure at different positions. Therefore, if the fruiting branch or fruiting mother branch is located at the top and grows vigorously, fruit drop is less; on the contrary, if the fruiting branch is located lower down or the branch is thin and weak, fruit drop is severe.
On the same fruiting branch, the fruit set in the middle drops the least, the top comes next, and the base drops the most. This is related to the degree of flower bud differentiation of the branch: the flower buds in the middle differentiate earlier and differentiate faster, so the fruit they bear drops less.
Physiological fruit drop mostly occurs from after flowering to mid-July, with the most severe fruit drop around the wheat harvest, accounting for about 80% of the total annual fruit drop; individual cultivars still have one more round of fruit drop in August to September.
2. Fruit drop caused by pests and diseases
First, the persimmon stem borer causes severe damage. The persimmon stem borer generally bores into the fruit around the wheat harvest; fruit damaged by the first generation does not easily fall off and will hang on the tree the whole time, with the larvae pupating inside and continuing to cause damage as the second generation. Fruit damaged by the second generation turns from yellow-green to orange-red, and easily falls off when it goes from hard to soft. Second, anthracnose causes damage. It occurs in the late growth period, generally breaking out in large numbers in September, causing fruit drop.
To prevent persimmon tree fruit drop, first, pollinator cultivars need to be provided, and pollinator trees must be planted or artificial pollination carried out. Second, during the flowering period, girdle the trunk or main branches of vigorous trees, with a width not exceeding 0.5 cm. For safety's sake, it is best to leave a safety strip or make a spiral girdle to facilitate healing. In addition, after girdling, the supply of fertilizer and water should be strengthened. Third, prune appropriately, especially strengthening summer pruning, removing useless and excess branches to promote ventilation and light penetration. Fourth, prevent and control pests and diseases, strengthen fertilizer and water management, and enhance tree vigor. Fifth, spray 500 ppm gibberellin at the flowering stage or young fruit stage, either alone or with 1% urea added, which has a very good effect on preventing fruit drop.
To prevent persimmon trees from dropping flowers and fruit, it is necessary to do a good job of pruning, fertilizer and water management, and pest and disease prevention, so that the persimmon tree can have a good growing environment and bear large, sweet fruit.