Key Technical Points for Autumn Management of Young Apple Trees
Young apple trees have relatively strong growth vigor but poor cold resistance. With poor management, they are prone to shoot shriveling after overwintering. In mild cases, growth is poor, the tree shape becomes disordered, and fruiting is delayed. In severe cases, the entire tree dies, causing missing plants and affecting orchard establishment. If autumn field management is strengthened to promote robust tree growth and well-filled, mature branches, overwintering ability can be effectively enhanced and dehydration shriveling can be prevented. The main autumn management measures are introduced below.
I. Training and Pruning
1. Pinching: From early August to early October, pinch off the tips of all shoots that have not stopped growing, to control branch growth, promote nutrient accumulation, and make the branches grow well-filled, robust, and mature, which helps them overwinter safely.
2. Branch bending: From early August to early October, to moderate tree vigor and balance branches and buds, continue bending all types of branches with small angles on the basis of branch bending in spring and summer, so as to open the angles. Generally, the angle of main branches is opened to 70—80 degrees, and that of nutrient-supplying branches to 90—120 degrees. When bending, pay attention: first support the base of the branch from below with one hand, then gently hold the base with the other hand and slowly bend it downward to prevent splitting at the base; the tying rope should be knotted in a “loose opening”. Achieve “no rebound” and “a single line” without circles, arches, touching the ground, or pointing skyward, so that the branch still forms a single line after bending.
3. Branch twisting: From early August to early October, while bending and pinching, twist the upward-growing branches on the main branches and auxiliary nutrient branches, and the vigorous shoots on the central leader, to change their growth vigor and growth direction. Method: use the hand to apply slight force from the base of the branch outward, gripping and squeezing the branch so that the branch tissue is damaged and the vascular bundles inside the branch emit a “pop-pop” sound, but the branch is not broken, and the leaves must not be damaged. After twisting, the branch is horizontal or drooping.
II. Use of Monopotassium Phosphate and Paclobutrazol
To promote well-filled, robust, and earlier-maturing branch growth and enhance the tree body and overwintering ability, after August, spray once every 10—15 days with 0.3—0.5% monopotassium phosphate and 1000—2000 mg/L paclobutrazol. The two can be sprayed at the same time, for three consecutive sprays.
III. Control of the Green Leafhopper
When the green leafhopper lays eggs on fruit trees in late autumn, it causes crescent-shaped wounds on the trunk. In winter and the following spring, water escapes from the wounds, which easily causes branches to lose water and dry out. From September 20 to October 20, spray once every 10 days with dichlorvos or deltamethrin at 2000—3000 times dilution, or fenvalerate at 2000—3000 times dilution, or pyrethroid pesticides, etc. Spray three consecutive times to control the green leafhopper. Whitewashing the trunk can also be used to prevent the green leafhopper from climbing the tree to lay eggs.
IV. Apply Base Fertilizer in Time
Finish applying base fertilizer in early September. At this time, after the base fertilizer is applied, the wounds of damaged roots can heal quickly, and part of the nutrients can be absorbed and utilized by the root system, increasing the nutrient storage of the tree body. Apply about 50 kg of farmyard manure per tree.
V. Stop Watering in Time
From August until before winter irrigation, do not irrigate with autumn water, so as to promote branch maturity.