How to manage fruit-bearing litchi and longan trees? A complete analysis of the key management points
I. Do a good job of post-harvest management 1. Harvest at the right time. When harvesting the fruit, use the two-cut method for each fruit: first cut off the fruit cluster together with the base of the fruiting branch, or even the base of the branch below the fruiting mother branch, and only then cut off the fruit cluster. How far back the branches below the fruit cluster are pruned depends on how well the branches of the fruiting mother branch have grown; prune back shorter for well-grown ones and longer for poorly grown ones.
I. Do a good job of post-harvest management
1. Harvest at the right time. When harvesting the fruit, use the two-cut method for each fruit: first cut off the fruit cluster together with the base of the fruiting branch, or even the base of the branch below the fruiting mother branch, and only then cut off the fruit cluster. How far back the branches below the fruit cluster are pruned depends on how well the branches of the fruiting mother branch have grown; prune back shorter for well-grown ones and longer for poorly grown ones.
2. Apply post-harvest fertilizer in time. After the fruit is harvested, apply a quick-acting fertilizer in time, mainly nitrogen fertilizer, together with phosphorus and potassium fertilizer, to restore tree vigor, promote the sprouting of autumn shoots, and lay the foundation for a bumper harvest next year. Taking a tree that bears 50 kg of fruit as an example, apply 1 kg of urea and 0.5 kg of potassium chloride per tree, broadcasting it with rain or applying it dissolved in water.
3. Clear the orchard and prune. Prune immediately after harvesting and fertilizing, cutting off diseased and pest-infested branches, shaded branches, crossing branches, and overlapping branches, and pruning back declining branches. After pruning, it is appropriate for longan to retain 10-15 shoots per sq m of tree canopy, and for litchi to retain 20-25 shoots. After pruning, dig two pits 1 m long and 30-40 cm deep and wide below the drip line of the tree canopy, bury the pruned branches and leaves and the weeds from the orchard at the bottom of the pits, then spread 0.5 kg of lime, and fill the upper layer with 5-10 kg of pig manure, 3-5 kg of Nongfeng biological organic fertilizer (produced by the Municipal Nongfeng Company), and 0.5-1 kg of calcium magnesium phosphate fertilizer mixed with topsoil, filling the pits to 10-15 cm above the ground, and finally spread lime powder on the ground for disinfection.
Spray pesticide once over the whole orchard to control diseases and pests. You can use 25% dimehypo at 500 times, or 90% trichlorfon at 600-700 times plus 64% sandofan at 600 times, or 40% chlorpyrifos at 1000 times, or Nongdile at 1000-1500 times plus 90% fosetyl-aluminum at 500 times.
4. Renewal of weakened trees. Carry out pruning back according to the degree of decline. For mildly declined trees, cut off the weakened branches and apply fertilizer evenly; for severely declined trees, prune back to larger side branches or even the main branches, and at the same time renew the root system and apply heavy organic fertilizer.
II. Fertilize rationally and cultivate timely, robust fruiting mother branches
Robust autumn shoots are the excellent fruiting mother branches of litchi and longan. Through scientific fertilizer and water management, rational fruit retention, pruning and bud thinning, and other comprehensive measures, cultivate robust fruiting mother branches. Strictly control the timing of shoot emergence so that the fruiting mother branches can sprout at the right time, mature at the right time, and normally enter flower bud differentiation. According to different varieties, tree ages, tree vigor, fruit load, management level, and climate characteristics, flexibly arrange the timing and number of shoot retention after harvest. Generally, trees of suitable age retain two batches of shoots, using the late autumn shoots as fruiting mother branches; vigorous mature trees retain one batch of autumn shoots. Taking Qinzhou City as an example, the more suitable time for the emergence of litchi fruiting mother branches is: for early-maturing varieties Heiye, Qinzhou Hongli, Xiangli, Nuomili, and Guiwei, in mid-to-late September; for Feizixiao and the late-maturing variety Heli, from late September to early October. Longan generally retains the shoots from late September to early October as fruiting mother branches, which mature from the end of November to early December and normally enter flower bud differentiation.
For medium and late-maturing varieties such as Heiye and Heli, the method of promoting and retaining two batches of autumn shoots on trees of suitable age: before and after harvesting the fruit, apply heavy nitrogen fertilizer (generally 1 kg of urea and 0.5 kg of potassium chloride per tree), so that the first batch of autumn shoots emerges in early July and matures before early September. In early-to-mid September, apply fertilizer before the second batch of shoots according to tree vigor, mainly compound fertilizer, appropriately increasing phosphorus and potassium fertilizer (generally 0.5 kg of urea, 0.5 kg of phosphorus fertilizer, 0.75 kg of potassium fertilizer, or 1-1.5 kg of compound fertilizer per tree), so that the second batch of autumn shoots emerges from mid-September to early October and matures from late November to early December.
Summer-extended autumn shoots and autumn shoots from short pruning are the most important fruiting mother branches of longan. Generally, only shoots with a diameter of 0.6-0.8 cm or more and with 12-15 or fewer compound leaves can become good fruiting mother branches. Therefore, the fertilization time and shoot retention time must be determined according to different tree vigor and fruit load in order to cultivate robust mother branches. For trees with a heavy fruit load and weak vigor, it is appropriate to add water and fertilizer and apply heavy fertilizer before and after fruiting, with the goal of forcing one batch of autumn shoots, with emergence in late September being the most suitable; for trees with a medium fruit load and medium growth, do not apply pre-fruit fertilizer, and through fertilizer and water regulation make the autumn shoots emerge from late September to early October; for vigorous trees with little or no fruit, it is appropriate to force two batches of autumn shoots, applying fertilizer and pruning in mid-to-late July so that the first batch of autumn shoots emerges in early-to-mid August and matures in mid-to-late September, then in mid-September apply another shoot-forcing fertilizer together with irrigation so that the second batch of autumn shoots emerges in early October and matures from late November to early December. This fertilizer is mainly quick-acting, high-quality nitrogen fertilizer; for a tree bearing 50 kg of fruit, apply 1 kg of urea and 0.5 kg of potassium fertilizer per tree. After harvesting the fruit, using water and fertilizer to force shoots gives the best effect.
III. Control diseases and pests in time
There are many litchi and longan diseases and pests in autumn, mainly stink bugs, Conopomorpha sinensis, leaf roller moths, eriophyid mites (felt disease), gall midges, longhorn beetles, scarab beetles, longan psylla, and longan witches' broom disease. According to climate conditions and the occurrence and development patterns of diseases and pests, use pesticides rationally at the right time, then spray once every 7-10 days thereafter, spraying 2-4 times per shoot. The pesticides can be selected from 52.25% Nongdile at 1000-1500 times, 48% chlorpyrifos at 1000 times, deltamethrin at 2000-3000 times, or methamidophos at 700-800 times.