Production practice has proven that Red Fuji apple trees have poorer cold resistance than Guoguang and Marshal. Therefore, in case of sudden cold weather, the winter temperature is too low, the duration is long, or the early spring cold weather, cold injury often occurs. The mechanism is: bark warming and freezing during the day, at night, the temperature is frozen, freezing and thawing alternately, quenching and sudden heat, resulting in damage and necrosis of the cortex. In areas where red Fuji is planted, it is an important task for fruit trees to recognize the symptoms of frostbite and to do a good job of preventing cold and freezing in Red Fuji.
First, the symptoms of frost damage
The cold tolerance of different parts and organs of Red Fuji apple tree is different. Generally, the cold endurance of branches and stems is the worst, and the cold resistance of the cortex and formation layers increases. Frozen frost damage to apple branches includes extensive freezing damage caused by the absolute minimum temperature in winter and frost damage caused by rapid changes in late autumn and early spring temperatures.
Perennial frost damage, most of the cortical local frostbite, dead tissue subsidence, browning. Perennial branching twigs or branches due to their poor cold resistance, the most vulnerable to cold, the performance of the cortex and forming layer after the browning depression, and the health of the boundaries. When the trunk is severely frozen, the bark cracks longitudinally, and the skin part curls up or curls outward along the crack.
The freezing damage of flower buds occurs in the warming period of spring, and the frozen flower buds show loose bud scales and become brown inside. During the budding stage, the buds do not germinate, they gradually dry up and die, or germinate weakly, and they do not flower.
Root and neck freezing injury showed that the cortex, forming layer became brown, rot, and easy to peel. If it is partially frozen, it will affect the tree potential, but it can still recover; if it is frozen in a circle, it will lead to the death of the whole tree.
Second, antifreeze measures
1. High-risk alternatives. Use cold-resistant root stocks to build gardens, and then make high-resistance at locations 70 to 90 cm above the ground to improve the cold resistance of Red Fuji apple trees.
2. After the promotion of control. Promote early growth, control late growth, make trees strong but not prosperous, stop growth in time, promote full ripening of branches, increase nutrient reserves, make Red Fuji trees have more time for cold-resistant exercise, improve the ability of the tree to resist cold. At the same time, during the whole period of dormancy, attention should be paid to changes in climate conditions in order to adopt appropriate preventive measures.
3. The use of anti-freezing agents or measures to strengthen anti-smuggling will also help to prevent frost damage in fruit trees. Practice has proved that spraying high ester film or carboxymethyl cellulose can effectively protect the saplings from overwintering, and has the effect of preventing drawing. High-ester film is a kind of macromolecule material. After spraying, it forms a protective film on the surface of the tree, which has the functions of preventing disease, resisting cold and resisting drought. 1 kilogram of high ester film 150 kilograms of water (first diluted with warm water plus enough water), from late February to mid-March, a total of 2 sprays, interval 15 days. Carboxymethyl cellulose has strong adhesiveness. After spraying, it can form a protective film on the surface of shoots, close the lenticels, reduce transpiration, reduce water consumption, and play the role of cold protection and heat preservation. Spray from 2 to 3 times from mid-February to mid-March, with a concentration of 100-150 times. Before use, the carboxymethyl cellulose is soaked with 5 to 10 times cold water for a day and night to form a paste, which is then diluted with water to the desired concentration.
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