First, fruit thinning: Artificial fruit thinning should begin 7-10 days after flowering and be completed within a month after petal fall. Trees with early blooming, high fruit set, poor nutrient management, severe disease, heavy fruit load, or weak growth should be thinned earlier. Conversely, varieties that bloom later, have low fruit set, heavier fruits, or lower productivity can be thinned later. When thinning, it's important to select well-shaped fruits, leaving more on long branches and those growing downward. Remove small, diseased, deformed, tip-growing, or short-stemmed fruits. This helps improve fruit quality and tree health.
Second, fruit bagging: For early-maturing varieties like Tsugaru, Dora, and some U.S. types, bagging should start 10–15 days after flowering. Red Fuji apples are typically bagged 15–20 days post-flowering, and the process should be finished before mid-June. Full-bag cultivation is recommended for Red Fuji, using both paper and plastic bags. Paper bags are best for the middle of the canopy, while plastic bags are suitable for upper, lower, and outer parts. You can also apply a plastic film bag first, then cover it with a double-layer paper bag to enhance fruit quality. The paper bag application should be done by early July.
Before bagging, 2–3 days prior, spray insecticides and calcium fertilizers thoroughly, focusing on the fruit clusters. High atomization is key, and heavy spraying is necessary afterward. During the bagging period, monitor for pests like codling moths and brown spot, as well as calcium deficiency. The number of sprays depends on weather conditions—usually 3–4 times per season. In rainy years, spray amino acid calcium fertilizer 2–3 times and add systemic fungicides like thiophanate-methyl or carbendazim. In drier conditions, use protective fungicides such as Taisheng or Bacteria. Also, control pests like bollworms, aphids, leaf miners, and caterpillars using pyrethroids, imidacloprid, or diflubenzuron.
After mid-June, when bagging is complete, spray a 1:2:200–240 Bordeaux mixture on the trees to prevent diseases like early defoliation and ring rot.
Third, managing fertilization and irrigation: The fruit bagging period is critical for young fruit development. Proper water and nutrient management supports fruit growth and reduces sunburn risk. After flowering, trees with heavy blooms, high fruit set, or weak growth should receive top-dressing with urea. From late May to mid-June, apply 15% compound fertilizer (NPK) at 50–75 kg per mu. Combine this with foliar sprays like 0.3% urea or amino acid micro-fertilizer to boost nutrient uptake.
Fourth, tree pruning: In mid to late May, avoid girdling main branches on apple trees like Zhuangwang or Fujia anthracoflorous long-branched Red Fuji. However, for varieties like Red Fuji and Red Star, if the tree is overly vigorous, you can prune every 10 days, even up to three times. For Wang Tzu, make 2–3 cuts 2–3 cm apart at the base of branches in mid-May to slow growth and encourage flower bud formation.
Remove excessive, dense shoots, especially around large wounds. Control vertical shoots at the top of branches and eliminate basal sprouts. Avoid over-pruning in summer, as it can weaken the tree. For young saplings, from late April to early May, cut back fruiting shoots and vegetative shoots to improve fruit set, especially for Zhuguang and Marshal varieties. For Changfu No. 2, from late May to early June, leave 20 cm of a single shoot and remove one of two pairs, keeping the other 20 cm to promote better fruit development.
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