What causes persimmon trees to drop their fruit?

The persimmon tree is a large tree native to the Yangtze River basin in China, and it is a fruit tree with a long history of cultivation in China. But persimmon fruit drop can seriously affect yields, so what causes this situation? How can it be prevented and controlled?

What causes persimmon fruit drop?

There are many causes of persimmon fruit drop, such as physiological fruit drop caused by incomplete flower bud differentiation, poor pollination, weather, unreasonable tree structure, insufficient fertilizer and water, and excessive soil moisture; or fruit drop caused by pests and diseases such as persimmon fruit borer and anthracnose.

How can persimmon fruit drop be prevented and controlled?

To prevent and control persimmon fruit drop, the following points should be done well:

1. Girdling at the flowering stage

Girdling can be carried out at any time from the initial flowering stage to the full flowering stage, and it is suitable for vigorous trees, vigorous branches or large fruiting branch groups. The width of the girdling cut is 0.3 to 0.5 mm; after girdling, wrap the cut with plastic strips to maintain the humidity of the cut and promote healing.

2. Reasonable summer pruning

During the growing season, remove dense branches and ineffective branches, leave more branches on the windward side and fewer on the leeward side, so as to promote ventilation and light penetration. After persimmon trees are generally pruned, latent buds will sprout in large numbers; to reduce nutrient consumption, useless sprouts should be removed before they become woody. For long branches with space to grow, especially water sprouts, pinch off the growing tips when they are 40 cm long.

3. Thinning flower buds

When 2 to 4 fruiting branches grow from a fruiting mother branch, keep the 3 flower buds in the middle of the first 2 fruiting mother branches, and remove all flower buds on the other fruiting branches, leaving them as reserve branches. When more than 5 fruiting branches grow from a fruiting mother branch, keep the first 3 fruiting branches to bear fruit, leave 3 flowers in the middle of each fruiting mother branch, and remove all the rest.

4. Skillful application of fertilizer and water

For large trees entering the full fruiting stage, fertilizer and water management should be strengthened. Apply base fertilizer early in spring and apply sufficient base fertilizer in autumn, but topdressing should not be too early. Generally, topdressing in May during the branch tip withering stage and in July during the fruit expansion stage can increase the fruit-setting rate, increase the number of flower buds for the next year and improve flower bud quality. Water should be given in dry weather.

5. Chemical regulation

Spray once each at the full flowering stage and the young fruit stage with 500 mg/kg gibberellin plus 1% urea, which can improve the nutritional status of flowers and fruits, prevent the formation of an abscission layer between the persimmon calyx and the fruit stalk, enhance the ability of flowers and young fruits to absorb nutrients, stimulate ovary expansion, and increase the fruit-setting rate. During the rapid fruit expansion stage, foliar spraying of 0.3% to 0.5% urea solution and trace element fertilizers such as ammonium molybdate can reduce flower and fruit drop.

6. Prevention and control of pests and diseases

During the growing season, manually remove diseased fruits and insect-infested fruits. In mid-June, spray once with 1:5:400 Bordeaux mixture, or 65% zineb wettable powder at 500 to 600 times dilution, or spray once with 2.5% green kungfu at 1500 times dilution plus 1.5% junlimei at 800 times dilution, which can prevent and control persimmon anthracnose, angular leaf spot, and circular leaf spot. In mid-to-late May and from late July to early August, when larvae peak, spray 20% methomyl EC at 2500 times dilution, mainly spraying the fruits, fruit stalks and flower buds of the persimmon tree, once every 10 to 15 days, for 2 to 3 consecutive sprays.

Therefore, to effectively prevent and control persimmon fruit drop, it is best to “prescribe the right medicine for the illness” according to the situation.