What are the key technical points for spring management of apple orchards?

I.   Orchard sanitation

In combination with winter pruning, saw off rotten and diseased dead branches, cut off branches with woolly apple aphid galls, and thoroughly clean the orchard. Clear away fallen leaves, dropped fruit, residual branches and rotting bark, then bury them in pits or burn them to reduce the source of pests and diseases. In late March, when the buds show green, spray to sanitize the orchard. The preferred pesticide is 5 degrees Baume lime sulfur mixture; alternatively, 45% Shennaning at 200-300 times dilution or other pesticides may be used.

II. Control of major pests and diseases

1. Valsa canker

Scrape clean both recurring and newly developed cankers. During scraping, the diseased tissue must be scraped off completely; the cut edge of the lesion should be smooth with no fuzzy stubble, and the scraping should be as deep as possible, reaching the xylem. After scraping, apply pesticide to the lesion, apply again after 7-10 days, then apply a 1-2 cm thick layer of mud and wrap with plastic sheeting. Commonly used pesticides include methylthiophanate-naphthaleneacetic acid healing agent, 843 rehabilitation agent, Fubiqing and other pesticides.

2. Hawthorn red spider mite

First, orchard sanitation. That is, in late March when the buds show green, spray to sanitize the orchard; the preferred pesticide is 5 degrees Baume lime sulfur mixture. Second, before flowering (inflorescence separation stage, early April), spray hexaconazole + abamectin + chlorpyrifos + organosilicon (also controlling powdery mildew, scale insects and other pests and diseases). Third, 10 days after flowering, spray Miesijing + emamectin benzoate-cypermethrin + imidacloprid + Xinling (also controlling aphids, leaf rollers, early defoliation disease and other pests and diseases). Fourth, in mid-to-late May, spray abamectin + propineb-mancozeb + imidacloprid + sugar alcohol calcium (also controlling early defoliation disease, aphids and other pests and diseases).

III. Flower and fruit management

1. Flower and fruit thinning

Flower and fruit thinning should be done early rather than late. Use the method of thinning inflorescences by distance and setting a single fruit, leaving one inflorescence about every 20 cm. Flower thinning begins after inflorescence separation, and fruit thinning begins two weeks after flowering, leaving one fruit per fruit spur.

2. Spraying fertilizer at flowering stage

At full bloom, spray the trees with 0.3-0.5% borax + 1% sugar + 0.3-0.5% urea to increase the fruit-setting rate.

IV. Topdressing and watering

In apple orchards at full fruit-bearing stage, in late March apply per mu 8-15 kg of pure nitrogen, 2-5 kg of P2O5, and 8-15 kg of k20, and water immediately after fertilizing.

V. Newly built orchards

When planting trees in newly built orchards, choose three-year-old large dwarfing interstock saplings as much as possible, with a plant spacing of 1.5-2 m and a row spacing of 4 m. Varieties can be chosen from Liangxiang, Jin Shiji, Huayu, Huashuo, Hongqian Fuji and other superior Fuji lines and superior Gala lines.