Management and remedial measures of Frost injury of Fruit trees

In winter, when the temperature drops below zero, some mismanaged orchards are often easily affected by low temperature, resulting in frost damage of fruit trees. After freezing injury, the absorption and transport of roots, leaf transpiration, photosynthesis and plant growth are all destroyed, so the management should restore the transport system as soon as possible, heal the wound, promote dormant bud germination and restore normal growth.

I. symptoms of frost injury of fruit trees

The main results are as follows: 1. root freezing injury: the root system grows underground, and the frost injury is not easy to be found, but the effect on the aboveground part is very significant, such as late or irregular germination in spring, and some are slightly affected by freezing injury, although they can sprout and shoot out, but grow slowly. in severe cases, the new shoots gradually withered and withered. After digging out the root system, it was found that the outer cortex turned brown, separated from the wood, and even fell off.

2. Root freezing injury: root freezing injury is caused by severe microclimate change close to the ground, the absolute minimum temperature is lower than the air temperature and the temperature difference is large, especially in the case of more stagnant water in the root and greedy green growth, the root freezing injury is more likely to occur. Sometimes freeze damage on one side of the rhizome, showing a ring brown and withered.

3. Freezing injury of branches: the trunk is broken, the branches are frozen, the cortex of the frozen branches is sunken or cracked, and the brown tissue is necrotic inside. In severe cases, the cortex and cambium at the base of the tissue are all frozen to death, and the injured branches wither, resulting in the decline or death of the tree.

4. Freezing injury of branches: the annual branches of fruit trees are more resistant to cold. The shoots that grow later and immature are the most vulnerable to freeze injury and dry up and die. Some branches look the same but sprout late, the leaves are thin or deformed, and the xylem turns brown after dissection.

5. Flower bud frost injury: flower bud frost injury mostly occurs in early spring, because the flower bud is released from dormancy, the temperature rises in spring, and when frost occurs, the flower bud suffers frost injury. When the freezing injury is mild, the sprouting is slow, deformed, or stay at a certain stage of development for a long time; in spring, it is not inflated, thin and easy to fall, and some of its appearance is not easy to see, but it can be seen inside that the bud pulp has turned brown and can die in severe cases.

II. Preventive measures for Frost injury of Fruit trees

1. Choose a suitable orchard: for newly developed orchards, choose places that are leeward and sunny as far as possible, so as to avoid building gardens on depressed terrain or shady slopes. Because in this place, the temperature drops early in autumn, the temperature is slow in spring, cold air stops accumulating at night in winter, and the accumulated temperature is relatively low.

2. Grass mulching in orchard: grass mulching can increase temperature and moisture, inhibit the growth of weeds, increase the content of soil organic matter, turn the soil deeply before grass mulching, apply sufficient base fertilizer, and cover with weeds after watering. It is about 20 cm thick and covered with a little soil, which can greatly reduce the degree of frost injury of fruit trees.

3. Strengthen fertilizer and water management: apply fertilizer before bud, mainly quick-acting nitrogen fertilizer and rare manure, use 0.3% 0.4% urea plus 1% Mo 2% calcium leaching solution and 4% plant ash extract for extra-root topdressing, and spray urea plus 0.3% potassium dihydrogen phosphate again 10 days later to promote the growth of new shoots and promote new roots. Suitable orchards should be irrigated in time to increase soil moisture and adjust soil temperature to prevent fruit trees from being frozen again. Practice has proved that reasonable fertilization and irrigation are not only beneficial to the growth of fruit trees, but also improve their ability to resist drought. The increase of organic fertilizer, phosphorus and potassium fertilizer is beneficial to the affinity of protoplast to water and strengthen the resistance of plants to adverse environment, which is beneficial to the overwintering and yield of fruit trees. Controlling irrigation and properly reducing the water content of plant tissue can also enhance the cold resistance of fruit trees.

4. timely and reasonable pruning: remove the dead leaves in time and prune the branches according to the frozen condition. Pruning principles are light pruning, leaving more branches and leaves, less flower buds, reducing load, promoting the growth of new branches, restoring and expanding the crown as soon as possible. In addition, newly planted young trees that die from freezing should be replanted before germination. Pruning can increase the yield of fruit trees, control the harm and spread of diseases and insect pests, enhance the accumulation of plant nutrients, and be beneficial to cold resistance and overwintering. Subtract the overcrowded branches to achieve ventilation and light transmission and control vegetative growth.

5. Spraying chemicals: some plant growth regulators can not only promote or inhibit the growth of fruit trees, improve yield and quality, but also enhance plant metabolism and regulate plant growth. Promote rooting and sprouting, improve the sugar content and coloring degree of fruit, and enhance the cold resistance and cold resistance of fruit trees.

6. timely prevention and control of diseases and insect pests: the body of frozen fruit trees is weak and their resistance is poor, which is easy to cause gum disease and rot in summer and autumn. the wounds of fruit trees should be smeared and disinfected with pesticides, and fungicidal pesticides such as carbendazim and carbendazim mancozeb should be sprayed in time to prevent the occurrence of diseases.

7. flower and fruit protection and reasonable load: for trees with frozen flower buds and few blossoms, measures should be taken to protect flowers and fruits, such as strengthening fertilizer and water management, artificial pollination, etc., to increase the rate of fruit setting; for those with a large amount of flowers and fruits, they should be thinned in time after freezing and the load should be reasonably controlled; for trees with weak tree potential and little or no fruit as far as possible, restoring tree vigor and increasing growth should be the main task.

8. Other measures: White tree trunks are coated with lime paste before winter, which can prevent and control diseases and insect pests and improve the ability of cold resistance and frost resistance. the young trees can also be protected by covering grass in the trunk or semicircular soil ridges in the north.