Detailed Explanation of Key Techniques for Autumn Cultivation of Longan

1. Restore tree vigor and enhance stress resistance. After several months of fruiting, longan trees have consumed a large amount of nutrients. The 4-month management period in autumn from August to November is a critical time for a bumper longan harvest the following year. Pre-harvest and post-harvest fertilizers for longan should be applied promptly to promote the swelling of longan fruit, increase longan yield and quality, and at the same time allow the longan tree vigor to recover early, enhance the stress resistance of longan, and lay the foundation for high and stable longan yields next year. For the specific amount of fertilizer, taking each tree producing 100 jin of longan fruit as an example, the pre-harvest fertilizer should be mainly quick-acting fertilizer 15 days before harvest, applying 2 kg of imported compound fertilizer per tree, applied after rain or when irrigating; the post-harvest fertilizer should apply 2 kg of ternary compound fertilizer and 100 kg of human excrement and urine per tree. The fertilization method is to dig a trench vertically below the edge of the canopy, 20-30 cm deep, cover with soil after application. Where conditions permit, it can be combined with one irrigation of the orchard to increase soil moisture, improve the fertilizer absorption effect of longan trees, and accelerate the recovery of longan tree vigor.

2. Cultivate fruiting mother branches to lay the foundation for a bumper and high yield the following year. The most ideal fruiting mother branch of longan is the last matured autumn shoot, so after fruit picking, water and fertilizer management of the mother tree should be strengthened promptly to promote the sprouting of autumn shoots and cultivate the autumn shoots into strong fruiting mother branches. Use water and fertilizer to control the uniformity of autumn shoot sprouting, which also facilitates orchard management and pest and disease control.

3. Pruning and training. In order to give the longan tree a good canopy and increase the yield per unit area of longan, the shaping and pruning of longan trees should be carried out twice a year. Spring pruning should be combined with flower and fruit thinning, and autumn pruning should be combined with post-harvest shaping of the tree form and canopy, retracting branches with excessive growth vigor (referring to young bearing trees), and pruning away weak branches inside the canopy, branch stubs just after fruit harvest, diseased and pest-damaged branches, and crossing branches, to improve ventilation and light penetration inside the canopy, restore longan tree vigor, naturally regulate the balance of endogenous hormones in the tree, and ensure the flower formation rate of longan the following year.

4. Pest and disease control. Autumn temperatures are suitable, so attention should be paid to pests such as longan psyllid, fruit borer, and Conopomorpha sinensis. For pest control methods, during the peak hatching period of larvae after forecasting, or at the early stage of new shoot sprouting, organize fruit growers to carry out comprehensive chemical control spraying. In combination with the control of other pests, use ① 20% fenpropathrin 2000 times or 10% imidacloprid 2000 times solution for spraying; ② 2.5% deltamethrin 2000 times solution for spraying, once every 15 days until the new shoots mature. For witches' broom disease, deep pruning of diseased branches should be adopted, and at the same time water and fertilizer management should be strengthened to cultivate thick and strong buds and shoots.

5. Renovate low-yield orchards. In autumn, temperatures fall back and longan root activity increases. At this time, low-yield orchards and neglected orchards should be treated with hole protection and soil improvement, increased application of organic fertilizers, improvement of orchard soil structure, increase of soil aeration, water retention, and fertilizer retention capacity, and enhancement of soil fertility. In addition to applying sufficient nitrogen, phosphorus, and potassium fertilizers, other trace element fertilizers needed for longan growth should also be applied. Trace elements should mainly be applied by foliar spraying to ensure the needs of longan growth and development at each stage. At the same time, the soil should be loosened, longan fibrous roots should be renewed, root activity should be improved, longan tree vigor should be rejuvenated, and strong fruiting mother branches should be cultivated to lay a good foundation for fruiting the following year.