A Detailed Guide to the Key Techniques for Four-Season Apple Tree Management

Among all fruits, apples are one of the more popular fruits with consumers. With the vigorous promotion of apple cultivation techniques, more and more fruit growers no longer rely on “heaven” to grant them a good harvest, but instead focus on applying apple tree cultivation techniques. Below, we share the four-season management techniques for apple trees.

I. Spring Management Techniques for Apple Trees

1. Pest and Disease Control Is the Most Critical

In spring, fruit tree valsa canker enters the peak period of primary infection for the year. Pathogens such as powdery mildew, early defoliation disease, ring rot, and anthracnose begin their first infection. Overwintering generations of pests, eggs, and pupae, including scale insects, golden leafminer moths, tortricid moths, aphids, and spider mites, also begin to emerge from dormancy and cause damage. At this time, carrying out pest and disease control work well plays an important role in reducing the base number of overwintering pest and disease sources and lowering the pressure of later control. Moreover, in this season, various pathogens and pests have poor resistance to pesticides, the leaves have not yet sprouted, there is no obstruction, spraying is convenient, and fruit trees will not suffer phytotoxicity.

(1) The best time for the first orchard sanitation spraying on trees is when the fruit trees are budding, that is, when the bud scales open and green tips are revealed. The focus of this sanitation spraying is to control trunk and branch diseases such as valsa canker and dry rot, as well as scale insects, cotton aphids, and green leafhoppers. Lime sulfur mixture can be chosen as the pesticide.

(2) The best time for the second orchard sanitation spraying on trees is from the red bud stage to the inflorescence separation stage. The focus of this sanitation spraying is to control powdery mildew, red spiders, aphids, tortricid moths, and so on.

2. Timely Supplementary Pruning Before Blooming Is the Key

Supplementary pruning before blooming is an effective measure to correct mistakes made in winter pruning and to compensate for tree shape damage caused by climate, mechanical injury, and other reasons. This measure can adjust the ratio of flower buds to leaf buds and coordinate the relationship between growth and fruiting. For young trees that have just begun to bear fruit, as many flower buds as possible should be retained for fruiting to moderate vegetative growth. For trees in full bearing age in an off year, more flower buds should also be retained to obtain a certain yield. For trees in full bearing age in an on year, the number of retained flower buds should be strictly controlled according to a flower bud to leaf bud ratio of 1:3 to 1:2. For main scaffold branches and branch groups with uneven vigor, adjustments can be made by retaining different numbers of flower buds: strong ones should retain more flowers, and weak ones fewer.

It should be noted that the apple flowering period often encounters low temperatures, strong winds, and late frost damage, which affect normal pollination and fruit set. Therefore, an appropriate number of extra flower buds should be retained, and fruit thinning should be carried out after fruit set.

3. Good Fertilizer and Water Management Is the Guarantee

On the basis of applying sufficient organic fertilizer, apply chemical fertilizer as a top dressing. Mix the chemical fertilizer evenly with Kejiejia high-activity humic acid powder and bury them together. At this time, applying Kejiejia high-activity humic acid can alleviate soil compaction, increase soil permeability, promote the growth of fine roots, and accelerate the root's nutrient absorption capacity under early spring low-temperature conditions, so as to meet the nutrient demands of fruit trees for flowering, fruit set, and new shoot growth; the amount of top dressing can be determined by soil, tree vigor, tree age, and yield.

In addition, from mid-to-late March to early April, watering should be carried out in combination with top dressing. Because the temperature is still low at this time, the irrigation amount should not be too large, so as not to lower the ground temperature and affect root development. For orchards that were not watered with winter freezing water before the New Year, watering should be done in time to facilitate fruit tree germination, flowering, and fruit set.

II. Summer Management Techniques for Apple Trees

1. Reasonable Top Dressing

Whether to apply top dressing to apple trees should be determined based on variety, fruit load, and earlier fertilization conditions. A top dressing of phosphorus and potassium fertilizer can be applied once, with potassium fertilizer as the main focus, and the amount applied depends on the tree. For early and mid-maturing varieties such as American No. 8 and Gala, top dressing should be applied in early July; for Red Fuji apples, try to apply top dressing once from mid-July to mid-August. Because July and August are in the rainy season, if the weather is not dry, watering may be omitted, and fertilization should be combined with rainfall.

2. Foliar Fertilization

In July and August, foliar spraying of phosphorus, potassium, calcium, iron fertilizers, and so on, in combination with pesticide use, plays an important role in increasing the sugar content of fruit, promoting coloring, and reducing physiological diseases of fruit. Commonly used fertilizers include superphosphate, monopotassium phosphate, potassium sulfate, plant ash, and ferrous sulfate. In production, monopotassium phosphate is mostly used in combination with calcium chloride, and the concentration used should preferably have a total salt concentration (total soluble fertilizer percentage content) not exceeding 0.5%.

3. Orchard Drainage and Weeding

During the rainy season, water must not accumulate in the orchard for a long time; otherwise, it will affect the soil permeability of the orchard and the root growth of apple trees. After rainfall, drainage should be carried out promptly to keep orchard soil moisture relatively stable. After watering or rainfall, hoeing and shallow cultivation should be carried out promptly to clear weeds in the orchard.

4. Regulating Tree Vigor

July and August are suitable for the vegetative growth of apple trees. In particular, young trees in the early fruiting stage and mature trees with few fruits tend to have vigorous summer and autumn shoot growth. If not regulated, this will affect flower bud differentiation, cause nutrient loss, disrupt tree shape, and reduce fruit quality. Therefore, appropriate measures should be taken to regulate according to tree age, tree vigor, fruiting conditions, and so on, so as to maintain healthy and vigorous tree growth. For vigorously growing trees, generally spray 150-00 times dilution of paclobutrazol once each in early and mid-July. For vigorously growing young trees that have not borne fruit or bear few fruits, a second trunk or main branch girdling can be carried out in early July.

At the same time, summer pruning work should be done well, with the focus on removing upright vigorous branches on the back, water sprouts in the inner canopy, competitive branches at branch tips, and useless branches that affect light. Twisting should be carried out on temporarily retained branches, so as to control excessive growth, improve light conditions, and promote fruit development and flower bud formation.

III. Autumn Management Techniques for Apple Trees

1. Do a Good Job of Autumn Pruning

For trees with excessive branch density, branch thinning should be carried out. The targets of thinning are crossing branches, parallel branches, overlapping branches, and competitive branches.

2. Apply Organic Fertilizer in Autumn

September is the best period for fertilizing apple trees and various other fruit trees. The best fertilization time is September, and at the latest it should not be later than early October. After the apples are harvested, apply it immediately. Chicken manure and sheep manure have high fertilizer efficiency, so the amount used should be appropriately reduced; crop straw has low fertilizer efficiency, so the amount can be appropriately increased while also increasing the amount of farmyard manure.

3. Harvesting Mid-Maturing Fruit

Remove bags from late-maturing bagged fruit. Fruit should grow inside the bag for about 100 to 110 days. For double-layer red fruit bags with an inner red layer, it is best to remove the bag in two steps. In high-altitude areas, fruit colors quickly, so the bag can be removed 15 to 20 days before normal fruit harvest. In low-altitude areas, fruit colors slowly, so the bag can be removed 20 to 25 days before normal fruit harvest. First remove the outer bag, then remove the inner bag within 3 to 5 days. When removing bags, it is best to choose an overcast or cloudy day. If removing bags on a sunny day, it should be done from 9 to 12 a.m. and from 3 to 7 p.m. When removing the inner bag, in the morning first remove the bags on the east side, north side, and inside the canopy; in the afternoon when removing bags, the southern and western halves of the canopy should be torn open into an umbrella shape to cover the fruit. Strictly avoid removing bags during high-temperature periods to prevent sunburn.

4. Leaf Removal and Fruit Turning

First cut off the leaves within 15 to 20 cm around the fruit that shade it or cling to it. After 5 to 6 days, remove the light-blocking leaves, small leaves, thin leaves, yellow leaves, and old leaves around the fruit, then remove part of the autumn shoot leaves and leaves on middle and upper branches that affect light penetration. Try to retain functional leaves so as not to affect photosynthetic efficiency. When removing leaves, first remove them from the middle and lower parts of the canopy and the inner canopy, then from the upper and outer parts of the canopy. In short, when removing leaves, the petioles must be retained, and the number of removed leaves should not exceed about 20% to 30% of the whole tree. Fruit turning is best carried out within 5 to 8 days after bag removal, when the colored area on the sunny side of the fruit reaches about 70%. Gently turn the fruit so that the shaded side turns to the sunny side. Do not use too much force, so as not to twist off the fruit. It is best to carry out fruit turning in 2 to 3 sessions.

5. Timely Spraying to Prevent Disease and Spraying Calcium Supplement Fertilizer

After bag removal, apple skin is delicate and highly susceptible to red spot disease, and the stomata enlarge, leading to cracking. In addition, calcium deficiency makes calcium deficiency disorders and other diseases highly likely to occur, and causes small cracks on the fruit surface, reducing the storability and market quality of the fruit. Therefore, after bag removal, spray 1 to 2 times with fungicide and calcium supplement fertilizer. For the fungicide, propineb 600 to 700 times dilution or thiophanate-methyl 1000 to 1500 times dilution can be chosen. Spraying potassium fertilizer at this time can prompt Red Fuji apples to color earlier and color well.

6. Lay Reflective Film Under the Tree

At the end of September or the beginning of October, immediately after the bags are removed from the apples, lay silver reflective film under the trees along the row direction, which helps the fruit in the inner canopy and lower half of the canopy color. Before laying, remove all weeds under the trees, level the ground, and pick up all hard debris. The film should be pulled straight and flat, and the edges should be pressed down firmly. After laying, frequently sweep the film surface to keep it clean and increase the reflective effect. Collect the film 1 to 2 days before harvest, wash and dry it, and store it for later use.

IV. Winter Management Techniques for Apple Trees

1. Clean the Orchard

Apples usually mature and are harvested in autumn, so after harvest, orchard sanitation work should be done well. Diseased branches and diseased fruit on the fruit trees should be pruned off in time. Weeds on the ground, diseased and disabled branches, and rotten fruit should also be cleaned up in time and taken out of the orchard for centralized treatment. This is because the pathogens of many diseases and various insect eggs lurk in these media to overwinter, and when temperatures rise in spring, they wake up and infect the fruit trees. However, fallen leaves of fruit trees can, depending on the specific situation, be deeply buried in the orchard soil to increase organic fertilizer in the soil, but the depth of deep burial must not be less than 60 cm.

2. Apply Sufficient Base Fertilizer

Applying sufficient base fertilizer is one of the basic measures to help apple trees overwinter. Applying sufficient base fertilizer not only helps fruit trees overwinter successfully, but also makes the following year's spring shoots and flower buds grow more robustly. When applying base fertilizer, the amount should be well controlled according to tree vigor, soil fertility, harvest amount, and other factors. Carrying it out together with plowing work can ensure that the soil receives fertilizer evenly, improve soil permeability, and enhance root respiration and nutrient absorption. Fully decomposed farmyard manure should be used as base fertilizer, and the depth at which base fertilizer is applied must not be less than 40 cm.

3. Water with Wintering Water

Apple trees enter dormancy in winter. Dormant fruit trees do not absorb nutrients or water, and the nutrients of the fruit tree gradually flow to the roots. Therefore, before the fruit trees enter winter dormancy, wintering water should be applied in time. This can not only ensure the fruit tree's water demand, but also promote the decomposition of base fertilizer. It is beneficial to the formation of new roots, improves nutrient absorption by the root system, and strengthens the assimilation of nutrients in the fruit tree. It can also promote flower bud differentiation of the fruit trees in the second spring. Therefore, during overwintering, the soil should be ensured to have sufficient water content to improve the flowering and fruiting rate in the second year.

4. Pruning Fruit Trees

Before the beginning of winter, pruning work for fruit trees should be done well to regulate the structure of apple trees and promptly remove water sprouts, excessively dense branches, overlapping branches, and so on. Enhancing the permeability of the tree body is conducive to improving nutrient accumulation in the tree and promoting flower bud differentiation of the fruit trees. However, when pruning, the pruning method should also be changed according to tree age. For example, for young trees, it is not recommended to prune off branches; instead, methods of cultivating the tree's framework structure can be used to regulate tree vigor. For mature trees, branches can be appropriately cut back to concentrate nutrients. After pruning branches, wounds should be protected well to prevent infection by pathogens that could cause pests and diseases.