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During the deep winter, the temperature dropped below 0°C. Some orchards that were cultivated or managed improperly were often vulnerable to low temperatures, resulting in frost damage to fruit trees. Frost damage of fruit trees is a common problem in northern fruit areas. Attention should be paid to prevention.
The symptoms of frostbite are not clear at a glance
Branches freeze damage. Late-growth, immature twigs, due to inadequate tissue, underdeveloped protective tissues, most likely to suffer freezing injury and die. Some shoots did not change from the outside, but they germinated late, the leaves were thin or deformed, the xylem was cut open and the color became brown, and then the black heart was formed. This was also a freeze injury.
Branches, neck and freeze injury. The cortex of the frozen twigs caved in or cracked, and the interior was browned to death. In severe cases, large branches died. The neck is frozen, and the cortex darkens. It usually occurs locally. When it is heavy, it forms a black ring surrounding the dry weeks, causing the entire tree to die.
Roots freeze damage. Roots grow underground and freezing damage is not easily detected, but the effect on the above ground is very significant. The phenomenon of budding late or irregular in the spring, or dry shrinkage after putting the leaves. Digging out the root system revealed that the outer cortex was brown, and the cortex was separated from the xylem and even fell off.
Flower buds freeze damage. Freezing damage of flower buds occurs mostly in early spring. Since flower buds are released from dormancy early, when the temperature rises and germination starts, and frost occurs again, it will cause frost damage. It is manifested as browning of flower buds, sluggish flower growth or malformation, affecting pollination and results, serious When the buds die and shrink.
Flowers (lei) freeze damage. If the flowering period encounters a low temperature below 0°C, it will cause frost damage. The first is that the pistil is browned, darkened and dried, followed by the stamens and finally the petals. As long as the pistil is frozen, it cannot pollinate the results.
Early prevention of comprehensive measures
Choose cold-resistant rootstocks. Choose rootstock seedlings with strong cold resistance, or use a strong cold-resistance rootstock to plant seedlings. For example, the mountain stator in apple rootstocks is more resistant to cold than the jellyfish.
Strengthen cultivation management. For a long time, attention should be paid to timely drainage of water, organic fertilizer should be used for fertilizer application, and additional phosphorus and potassium fertilizers should be used to control the amount of nitrogen fertilizer (especially in the middle and late stages of fruit tree growth, with little or no application). This will prompt the fruit tree to end its growth prematurely and enter a dormancy period.
Winter irrigation. In the winter before the soil is frozen, the water is poured and sealed with frozen water. Before the early spring, the fruit trees are watered before sprouting to prevent drought, reduce the temperature, delay the sprouting and blooming of the fruit trees, and achieve the purpose of preventing frost damage during the flowering period.
Reasonably trimmed. In winter, care must be taken to cut off immature shoots. When large branches are removed, protective agents can be applied to the cut-off cuts to prevent cuts from freezing due to low temperatures.
Saplings prevent cold. The newly planted saplings are best to be buried in cold weather, can not be bent down, should be piled up around the root conical mound, about 30 cm high and practical, in order to prevent the wind, and then covered with a layer of dry fine soil, with moisture evaporation . If you can't bend down, you can also build a half-moon crescent with 60-70 cm in length and width in the northwest of the trunk about 50 centimeters from the trunk to change the microclimate around the tree, increase the soil temperature, and shorten the soil. During the freezing period, the roots of the fruit trees absorb the water in the soil in time to reduce or prevent the drawing.
Bundle the straw. Before winter, using a straw or straw rope around the trunk or main branch can not only prevent the cold wind from invading, but also reduce the water loss from the trunk. After the sprouting in the spring, the tied objects are released and burned or buried deeply to eliminate the overwintering pests and diseases.
The trunk is white. After the fruit trees are defoliated, the trunks and main branches of the fruit trees are evenly painted white, so that the temperature of the tree body changes stably, and there will be no freeze-thaw, no-freezing, no frost, no sunburn, and the killing of pathogens and eggs hidden in the trunk. And adults. The proportion of whitening liquid is: 100 parts of quicklime, 10 parts of sulfur powder, 10 parts of salt, 1 part of vegetable oil, and 200 parts of clear water (by weight).
Orchard smoke. In the low-lying orchards where cold air is easy to gather in winter, the method is particularly effective. The practice is that in the evening before the onset of the low-temperature cold wave, firewood, chopped weeds, sawdust, clam shells, waste kerosene, etc. are used as fuel. The temperature drops to the critical temperature when the fruit trees are frozen, and the smoke is controlled so that the smoke is covered. In the space within the orchard, generally, 4-5 fire points can be set per acre of fruit trees, with 15-20 kilograms of material per pile, and they should be set at the upper tuyere.
Spray salt water before flowering. Before the buds sprouted, the trees were evenly sprayed with 1% saline, which could effectively improve the anti-freezing ability of the tree itself and prevent flowering frost.
Spray growth regulators. Naphthylacetate (250-500 mg/kg) solution was sprayed on the whole tree before germination to inhibit sprouting and delayed flowering for 3-5 days.
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