What are the technical measures for flower and fruit retention in mango?
The flowering and fruit-setting period of mango is an extremely critical period in mango production management. The management measures during the flowering and fruit-setting period include the following aspects:
1. Training of flowering shoots. About 2 months before flower bud differentiation, remove overly dense branches, shaded weak branches and diseased and pest-infested branches, leaving only 1-2 shoots per branch, which can increase the light penetration of the canopy, help concentrate nutrients and create good ventilation and light conditions, promote flower bud differentiation and prevent the occurrence of pests and diseases.
2. Cultivating and attracting flies for pollination. Before flowering in a longan orchard, piling up garbage or composting bran manure, chicken manure, salted fish scraps, poultry and livestock viscera, etc. in the orchard can cultivate and attract flies to come to the orchard to reproduce and pollinate. However, using flies can only provide partial pollination.
3. Application of trace elements and calcium fertilizer. From flowering to the young fruit stage of mango, applying lime can reduce soil acidity and the content of harmful iron, aluminum and manganese, and raise the calcium level. Generally, apply 0.6-0.8 kg of lime per plant, or spray a 2% calcium chloride solution from flowering to the fruit-setting stage. For the application of zinc and boron, spray a 0.2% zinc sulfate and 0.2% borax solution once 10 days before flowering and at full bloom and after flower drop, to promote pollination and fruit set. When applying, it can be mixed into pesticides during pest and disease control for foliar fertilization, and combined with irrigation. For soil application, apply 100 g of zinc sulfate and 50 g of borax per plant before the autumn shoots sprout, in combination with nitrogen, phosphorus and potassium fertilizers.
4. Spraying flower and fruit retention agents: use 50-100 ppm gibberellin, spraying once every 15-20 days after flower drop, for a total of 2-3 sprays, which has a certain effect on increasing the fruit-setting rate. Or use the following method: full bloom stage: spray 50-70 PPm of fruit-setting hormone (produced in Sichuan) + 0.3% borax. 1 week after flower drop: spray 50-70 PPm of fruit-setting hormone (produced in Sichuan) or 300 times Duoxiaohao or 0.5-1 ppm of 1.8% Aiduoshou + 0.2% monopotassium phosphate. 2-3 weeks after flowering: spray 30-50 ppm “920” plus 0.3% urea.
5. Topdressing. (1) Rhizosphere topdressing: from after flower drop to the rapid expansion stage of young fruit, topdress according to tree vigor and fruit load. Fertilization is mainly nitrogen and potassium fertilizers. For trees under 10 years old, apply 0.3-0.5 Kg each of urea and potassium fertilizer per plant; for trees over 10 years old, apply 0.5-1.0 Kg each of urea and potassium fertilizer per plant; for trees with few fruits, nitrogen fertilizer may be omitted and only potassium fertilizer supplemented, applying 0.3-1.0 Kg of potassium fertilizer per plant depending on tree age. During fruit growth, for weak trees with many fruits, an appropriate amount of nitrogen and potassium fertilizers can also be supplemented in June. (2) Foliar topdressing: spray 0.3% boric acid and 0.2-0.3% monopotassium phosphate once each at full bloom, at the end of flowering, and at the young fruit stage.
6. Fruit thinning and pruning of fruit-bearing branches. Fruit thinning is carried out within 15-30 days after flower drop, when the young fruits are the size of peanut grains, keeping only 2-4 fruits per cluster, preferably in the central position, selecting larger young fruits with tender green color and strong growth vigor, with the retained fruits evenly distributed within the canopy and among branches, preferably so that the fruits do not press tightly against each other. After physiological fruit drop in mango, the rachis is difficult to fall off naturally and should be cut off manually to avoid wind scraping and damaging the fruit skin and affecting appearance. However, the Irwin and Jinhuang mango varieties should be retained.
7. Promoting coloring. For some varieties with good red peel, such as Hongmang No. 6 and Irwin mango, during pruning at the mid-fruit stage, remove shaded weak branches, diseased and pest-infested branches and other branches that block the fruit, so that each fruit receives sufficient light and colors evenly. Before bagging the fruit, spray 1-2 times with 70% dithianon wettable powder, which can make Irwin mango have a rosy appearance color; spraying 50% benomyl wettable powder can promote tender fruit skin and produce bloom; spraying 80% sulfur wettable powder can promote red-yellow color on the fruit skin and produce bloom.
8. Bagging. The fruit development period of mango is a time of high temperature and abundant rain, and fruit bagging is the best way to protect the fruit from pests and diseases. Before bagging, spray fungicides and insecticides first, or the paper bags can be dipped in the medicinal solution and used after soaking, then tied tightly after bagging, with a drain hole left at the bottom of the bag to discharge accumulated water. The size of mango bags varies by variety, with general specifications of: length 22-30 cm, width 15-20 cm; the paper bag material can be composed of white wax paper, black kraft paper and non-woven fabric. The bagging time is generally after fruit set is basically stable, that is, after the second physiological fruit drop ends, when the fruit grows to the size of an egg. Zihua mango is bagged about 35 days after flower drop, and Irwin mango is bagged 30-50 days before harvest, which is beneficial for fruit coloring. Jinhuang mango can be bagged earlier, or bagged 45 days before harvest.