Freezing damage is usually below 0°C during wintering, and fruit trees often exhibit cell injury or death.
Frost damage type: First, the tender shoots freeze damage, stop growing later, the development of immature shoots, because the organization is not full, the underdeveloped protective organization, easy to freeze and die.
The second is the cold damage of the branches. The cortex of the frozen twigs is subsidence or cracking. The inside is darkened by browning and the tissues are dead. In severe cases, the large branches also die.
The third is the freezing damage of branches, the development of normal branches, although the cold resistance is stronger than the twigs, but there will be freezing damage when the temperature is too low, some branches look no change, but late germination, thin or deformed leaves, abnormal growth , Cut open the xylem color brown, after the formation of black heart, which is caused by frost damage, in serious cases when the entire branches dry dead.
The fourth is freezing and chilling of roots and stems. The roots and cortices darken and die, lightly occurring in the local areas, and heavy in the formation of black rings. The whole plant is dead.
The fifth is that the root system is cold-freeze. The cold damage to the roots growing in the ground is not easy to find, but the effect on the above-ground parts is very significant. It shows that the buds are late or irregular in the spring, or the phenomenon of shrinkage occurs after the “spreading leavesâ€. In the root system, the outer cortex turns brown, and the cortex separates from the xylem and even falls off.
Preventive measures: First, to strengthen fertilizer and water management, rational fertilization and irrigation are not only beneficial to the growth of fruit trees, but also improve the cold resistance of fruit trees.
The second is rooting the roots and stems. During the wintering period, the rhizomes are sealed with mounds and covered with grass, which can effectively prevent the rhizomes from freezing.
The third is spraying cold-preventing agent, spray cold-applied spray-applied herbicide, anti-reverse production agent, and biogas slurry before winter, which can improve the cold resistance and frost resistance of fruit trees.
The fourth is reasonable pruning, which can not only improve fruit tree yield and quality, enhance tree nutrient accumulation, but also reduce the frost damage of fruit trees.
Frost frost refers to the phenomenon that when the temperature near the soil surface or the crown of a plant falls below 0°C in a short period of time, the agricultural and forestry crops are subject to freezing injury. When a crystalline frost comes along, it is called a "white frost." When there is no crystalline frost, and the agricultural and forest crops also suffer from frost damage, they are called "black frost." When frost occurs, the method of defense against frost can be covered, ie, covered with leaves, straw, etc. in the orchard. Smoke can also be used, that is, when the measured temperature drops to nearly 0 °C (usually 2 °C ~ 3 °C), the "smoke" (straw, weeds, etc.) can be ignited to form a thick smoke, so that Frost is difficult to form; it can also use the leaching (dissolving) water method, that is, irrigation or watering the orchard to increase the heat capacity, is conducive to prevent frost.
Sunburn due to the sun during the winter sun exposure, the temperature of the fruit branches dry, thawing the frozen cells at night, freezing and thawing alternately, so that the cortical cells are damaged, promote bark discoloration into a patchy, severe phloem and xylem detachment. The most effective method of prevention is to whiten the trunk, reflect the sunlight, relax the bark, change the temperature drastically, and reduce the surface temperature of the shoots.
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