Detailed Explanation of Key Apple Tree Management Techniques for Spring 2020

After the autumn harvest, apple trees enter a dormant period in winter. The dormant period refers to the period from natural leaf fall in late autumn and early winter to bud break in the following spring. So, what are the key apple tree management techniques for spring 2020?

1. Fertilizing during the flowering period

Supplement part of the nitrogen fertilizer, with the application amount accounting for about one quarter of the annual total, that is, 22 kg of urea per mu. If conditions permit, an appropriate amount of potassium fertilizer should be applied, with 200 kg of plant ash or 16.5 kg of potassium chloride per mu, applied by the radial trench method or strip trench method.

2. Irrigation from bud break to before flowering

If there is local spring drought, irrigate once. Irrigation is needed when soil moisture is below 60% of field capacity.

3. Intertillage to conserve soil moisture

After fertilizing, carry out intertillage throughout the orchard, break up clods and rake level, and loosen the soil after irrigation to conserve moisture.

4. Supplementary pruning before flowering

① Bend branches to open the angle: for spindle-shaped trees, bend the small main branches to 70-80 degrees and spread out the auxiliary branches;

② For trees with abundant flowers, thin and cut back branch structures that affect light, and cut back flower-bearing branches with clusters of flowers by retaining 3-4 flowering branches; lightly head the medium fruit branches and retain vigorous short fruit branches for fruiting. When there are insufficient flowers, retain as many flowers as possible, and thin and cut back branches that have no flowers but were left in excess; ③ Properly cut back branches that were left unpruned in previous years and have already formed flower buds; ④ For trees planted at relatively high density whose crowns have already met, properly cut back and reduce crown height and width.

5. Flower thinning

① Manual flower thinning: carry out from bud stage to petal fall, retaining flowers reasonably according to tree vigor, generally leaving one inflorescence with only a single flower every 15-20 cm;

② Chemical flower thinning: for Yuanzhong series, spray 1000-2000 ppm carbaryl 2 weeks after full bloom; for Golden Delicious types, spray 10-20 ppm naphthaleneacetic acid after full bloom; for Ralls and Fuji types, spray 1500-2000 ppm carbaryl after full bloom, or first spray 300 ppm ethephon at the bud stage, then spray 300 ppm ethephon + 20 ppm naphthaleneacetic acid after flowering.

6. Pest and disease control

① Control of powdery mildew, leaf roller, and hawthorn red spider mite

Before flowering, spray 50% sulfur suspension concentrate at 150-2000 times mixed with 25% parathion capsule suspension at 800 times, or 40% isocarbophos at 2000 times, or 20% fenpropathrin at 3000 times. During the flowering period, spray a mixture of 300 times borax plus 500 times urea 2-3 times.

② Control of apple early defoliation disease, ring rot, anthracnose, moldy core, and peach fruit borer

10-15 days after flowering, that is, during the rapid growth period of young fruit, spray 1:4:200 Bordeaux mixture, or 50% carbendazim at 700 times, or 50% thiram at 700 times. For young vigorous trees, spraying the ground with 50% phoxim at 200 times or 25% parathion capsule suspension at 200 times can control peach fruit borer.

The key to management during the dormant period of apple trees is to maintain the assimilation function of the leaves well and prevent early defoliation. The quality of management during this period also directly affects the tree's winter cold resistance and the quality of flower bud differentiation, and plays a decisive role in the following year's flowering and growth. In addition, the quality of spring management of apple trees also directly affects the yield and quality of the fruit that year.