Freezing damage has always been a common cause of damage to fruit trees. Apple trees are even more so, and apple trees are perennials. Once frost damage occurs, their effects are long-lasting. A series of rot diseases caused by frost damage also make farmers quite headaches. Below, the cause of apple freeze damage and control measures will be summarized.
1. Shoots: Shoots and shoots grow late, and they are immature and unorganized. They are prone to freeze injury and die. In terms of appearance, there are no major changes in the branches, but the interior will turn dark brown, causing serious black hearts. This frostbite will not immediately die, but because the xylem catheter is blocked, can not open the water, the lack of nutrients stored inside the shoots, late germination, leaves thin or deformed, abnormal growth, the formation of similar lobular branches, it will slowly death.
2. Flower buds: The temperature in the deep winter season is unstable, and the short-term warming causes the cold resistance of the flower buds to decline. Cold winter or hot and cold temperatures often cause flower buds to freeze and damage. Freezing of flower buds is characterized by browning of internal scales, darkening of the stigma, and death of the entire flower bud when severe.
3. Root neck: The root neck refers to the junction between the base of the trunk and the root system. The root neck enters dormancy later, and the dormancy is released earlier. Near the surface, when the temperature is low and the cold resistance is weak, it is the main cause of root and neck freezing injury. . Root-neck freeze injury is characterized by darkening of the cortex at the root neck and death, ranging from local to mild, with formation of a black ring and surrounding the stem, causing death of the whole tree when it is too severe.
Root system: The main cause of frost damage in the root system is that there are many root systems under the ground and the surface is floating, the surface soil is too loose or sandy soil, and the winter is too cold or the cold winter lasts for a long time. The frost damage in the root system showed that the outer cortex was dark brown, and the cortex was separated from the xylem. Severe detachment occurred completely. When the root soil temperature reached -12 °C to -16 °C, the apple roots began to freeze.
Prevention
One: Wrap the trunk. Before the large-scale frost damage, use wheat straw and straw rope to wind the trunk, main branch or grass to bind the trunk to prevent the cold wind from invading and reduce the freezing injury. When weeding the grass, the top of the grass should be tied to the trunk with a rope and spread out below. Do not tie the grass tightly to prevent the trunk from freezing and freezing.
Second, trim. In late autumn or early winter season, the deciduous fruit trees, especially the 1-2 year old deciduous fruit trees, can be properly pruned or artificially defoliated to reduce tree consumption, increase accumulation, and improve cold protection and antifreeze capacity.
Third, white trunk. In the late autumn and early winter, the trunk was painted white in conjunction with the clear garden. First, 5 kg of quicklime and 1 kg of salt are melted separately with 20 kg of hot water, and then the two liquids are mixed and stirred, and 0.5 kg of raw liquid of lime sulfur mixture and 0.1 kg of vegetable oil are mixed to make whitening agent. One is the overwintering pathogenic bacteria and eggs that can kill the trunk; the second is to enhance the solar reflection ability, reduce the large changes in the temperature difference between day and night, and avoid sunburn and freezing overnight. When dry, the trunk should be completely covered until the main lateral branch of the childbirth.
Fourth, winter irrigation antifreeze. One and a half months after fruit picking, when the soil “frozen in the night,†the trenches were dug between the fruit trees, and then the water was poured along the ditch. It is better to see the amount of water seeping before nightfall. It can not only achieve winter water use, prevent spring drought, promote the growth and development of fruit trees, but also can store water and keep warm, so that the ground temperature during the cold wave is relatively stable, so as to reduce the freezing injury. After the winter irrigation, it is better to cover the grass or shallow the surface to prevent evaporation of water.
5. For the apple trees whose trunks are completely frozen and have a complete root system, the above-ground parts can be sawed off. In the third year of April and the following year, they were grafted again using splicing or subcutaneous grafting. If the trunk of the sapling is chilled, the saplings can be re-emerged, leaving a robust sprout and reculturing the tree.
Sixth, if the tree trunks account for more than half of the apple trees, they are bridged on the frozen side. Serious damage must be re-grafted.
Seventh, the lighter damaged apple tree, before germination, spray 100 times more effective rot to prevent rot. After germination, the dead bark was scraped off and coated with 843 rehabilitant or rot star liquid. Branches were sterilized during the apple tree growth period with a treatment for rot disease, once every two weeks. 7 to 10 days after the leaf is sprayed, a small amount of urea is added to the vital acid, and sprayed for 4 to 5 times. In the pruning, in addition to cutting off the frozen dead sticks, the wound should be reduced as much as possible, and the principle of light shearing should be used to slowly put part of the shoots and retract the extended branches to extract the Wang branch.
Eight, apple bud victims, the top buds, side buds all frozen, to increase the amount of fertilizer, timely water supply, promote budding, bud germination, re-cultivation sticks.
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