This paper analyzes the causes and manifestations of freezing injury of figs, and puts forward scientific preventive measures to improve the quality.

Figs are common deciduous fruit trees in the north. Its fruit is rich in nutrition and is loved by many people. It has a good market prospect, but compared with other deciduous fruit trees, it has weak cold tolerance and is prone to freezing injury. Freezing injury not only affects the yield and quality of figs, but also causes economic losses to fruit farmers in different degrees. Based on the production practice and continuous observation of figs in the open field in recent three years, this paper analyzes the causes and manifestations of freezing injury of figs, and puts forward scientific preventive measures. In addition, targeted remedial measures are put forward for freezing damaged trees, which provides scientific and technical reference for fruit farmers' efficient production:

1 causes of freezing injury

?

? 1. 1 low temperature

?

? Low temperature is the direct cause of freezing injury of fig. When the temperature is lower than -5℃, the new shoots of fig may suffer from freezing injury, and when the temperature is as low as -7- 15℃, some branches on the ground may freeze to death. When the temperature is-16-25℃, the root system may be frozen, resulting in the death of the whole plant.

?

? 1.2 variety

?

? Different varieties (lines) of fig have different degrees of resistance to freezing injury. Generally speaking, varieties such as Green Peel, Blank and Bojihong have better cold resistance. When the temperature is below -5℃, the branches will not be frozen, while when the temperature is around-10℃, the twigs will be frozen. But at -3-5℃, the branches above the trunk will freeze.

?

? 1.3 age

?

? The cold resistance of fig is closely related to the age of the tree. The cold resistance of 1-3-year-old young trees is the weakest, and it gradually increases with the increase of tree age. Under normal circumstances, seedlings of green tangerine peel, Blank, Bojihong and other varieties planted for one year need to be cultivated and frozen after fixation. Young trees of 2-4 years old can be bound with plastic or grass to prevent freezing, and fruit trees of more than 5 years old can overwinter safely without protection. Varieties with weak cold resistance, such as Maisiyi peach powder, can cause serious freezing damage when young trees meet the low temperature of -3-0℃ and adult trees meet the low temperature of -4-8℃.

2 Judgments and manifestations of frostbite

?

? 2. 1 terminal bud plumpness and branching toughness

?

? Observe whether the terminal buds on the branches of fig are round and full, and whether the branches within 25cm below the terminal buds have strong natural toughness. If the terminal bud is dry, it means it has been frozen. If the branch is biennial, the epidermis is discolored, necrotic and sunken, and you can't feel the inherent toughness when you bend it gently with your hands, it is frozen.

?

? 2.2 The trunk is cool and smooth.

?

? Touch the trunk with your hand to see if it feels cool and smooth. If there is, it means there is no frostbite. Otherwise, the tree is frozen. Especially in winter, when the temperature drops suddenly, the cortex tissue of the trunk shrinks rapidly, and the xylem generates stress to make the bark open, and the intercellular space freezes, resulting in cracks, which are mainly manifested as the bark shrinking, the color turning brown or brownish white, and the trunk bark cracking longitudinally. In severe cases, the bark turns outwards and the cracks reach the xylem, which leads to the dry trunk of fig and death.

?

? 2.3 Man-made carved wound inspection

?

? Manual scratch inspection should be carried out in early spring after fig trees overwinter. Use hacksaw, saw blade and other tools to draw a longitudinal wound 1cm from top to bottom on the lower part of the terminal bud, not too deep, and the broken skin can reach the xylem. If the soil is full of water, the liquid will flow out soon. On the other hand, if the soil is dry, liquid will flow out within 10h at the latest, so it can be confirmed that the tree has wintered safely.

?

? 2.4 Excavation and Root Inspection

?

? Ficus carica is a shallow-rooted fruit tree, and its roots near the surface are vulnerable to freezing injury, especially in the dry sandy land with little snow in winter, but it is often difficult to find out the root damage in time. A deep pit of 30-50 cm can be dug around the fig tree. If it is found that the fibrous roots are black, the main lateral roots are dark brown or brown, and the root epidermis can be easily twisted by hand, then the whole tree can be judged dead. If the fibrous roots are yellowish white, the main lateral roots are milky yellow or white, and the root epidermis is firmly attached, it can be judged that the upper part of the tree has been frozen, but there is no damage below the trunk.

?

? 3 measures to prevent freezing injury

?

? 3. 1 Selection and planting of cold-resistant varieties

?

? Different varieties (lines) of fig have different cold resistance. When choosing planting varieties, we should not only consider the flavor, maturity and economic benefits, but also pay attention to the adaptability and cold resistance of varieties. Usually, when planted in the open air in the northern region, varieties with relatively strong cold resistance such as Green Peel, Blank, Japanese Purple Fruit and Bojihong should be given priority, while varieties with poor cold resistance such as Maisiyi Taofen and Hongsama should be planted cautiously. For fig cultivated in protected facilities, the cold resistance of varieties can be ignored, and only the difference between fruit quality and market demand can be considered.

?

? 3.2 Strengthen management and improve the wintering ability of trees.

?

? After autumn, fig trees should properly control the supply of nitrogen fertilizer and water, ensure the enrichment of branches, and strengthen the accumulation of nutrients in the tree, so as to improve the cold resistance of the tree itself, and avoid causing the branches to grow too long and not be enriched, and sprouting many invalid auxiliary branches, which will lead to the decline of the cold resistance of the tree. Before entering winter, water for wintering should be poured in time, and it must be poured before the soil freezes, and the water should be filled at one time. The watering time of overwintering water should not be too early. Generally, it is best to water during the period of "daily chemical freezing at night", so that when the soil is completely frozen, a relatively stable frozen soil layer will be formed around the tree disk, which is conducive to maintaining the relative stability of the root temperature and preventing the root from freezing due to the fluctuation of weather temperature.

?

? 3.3 Winter packaging protection

?

? Planting a square mound with a width of 40-60cm and a height of about 20cm at the root of fig tree can effectively prevent the trunk and root from frostbite at low temperature. The next spring, the time of moving the soil should be appropriate, neither too early nor too late. Generally, after late frost 10d, when the ground temperature is stable at 4-6℃, the soil can be scraped off. For dead branches and fruiting branches, you can immediately roll up straw ropes to dry or wrap them with plastic and straw to prevent freezing. Specifically, when the grass is wrapped around the branches, the tips of the grass bundles are concentrated upwards, and half of them are buried in the soil. Then, the grass bundles are tied up with a straw rope, and the grass bundles are continuously wrapped upwards, and tied firmly every 15cm, and the grass is tied to each branch layer by layer. When it snows in winter, it is necessary to clear the snow on the branches in time to avoid that the snow pressure is too long and too heavy, causing the branches of figs to bend, making it difficult to restore the tree shape, and even causing some branches to break or split.

?

? 3.4 Spraying antifreeze

?

? Before the arrival of the cold wave in June 5438+065438+1October and when it was cold in June 5438+1October of the following year, the antifreeze for fruit trees was sprayed, which was mainly composed of paraffin, vegetable oil, polybutene, fulvic acid, salicylate and guaiacol, and it was sprayed 800-/kloc-0 for two consecutive times. Trunks and branches can also be painted 50- 100 times, which can effectively avoid freezing injury. Attention should be paid to adjusting the concentration of antifreeze according to the local weather forecast. When the cold current is strong, the concentration should be large when preparing, which can effectively prevent the freezing injury of trees.

?

? 3.5 park smog

?

? Smoking is a common method to deal with freezing injury, and the preventive effect depends on the quality of raw tobacco. The temperature of high-quality orchards can be raised to 2-4℃. Smoke can be sawdust, crop stalks, weeds, fallen leaves and other flammable substances that can produce a lot of smoke. The number of raw smoke piles is at least every 667m? Set 5-6 piles, evenly distributed in all directions. The pile height is 0.6m, and the bottom diameter is1-1.5m. When stacking grass, several thick sticks are inserted directly or obliquely. After burning the pile, take them out as ventilation holes, put sawdust into the pile from the holes, and cover the pile with a layer of wet grass or mud, so that the smoke is enough and the time is long. Pay attention to control the fire and avoid smoking and baking trees. It is advisable to smoke with dark color, which has a significant effect on preventing low temperature above -5℃.

?

? 3.6 Improve local microclimate

?

? When planting figs, we should pay attention to choosing places with sunny lee and good natural microclimate conditions, planting windbreaks or setting wind barriers in the windward direction of the park. Wind-resistant trees with large crowns and deep roots are generally planted in windbreaks, and willow is the best. The specific way to set up the wind barrier is to set up the wind barrier in the windward direction of the tree. The material of the wind shield is usually corn straw. In order to keep the wind strong, the straw should be tied with bamboo poles and iron wires horizontally. The height of the wind wall is higher than that of the fig tree. The windbreak wall is buried 0.5m deep underground, and both sides are usually supported by wooden stakes to prevent it from being blown down by strong winds, which can effectively reduce the wind speed and improve the local microenvironment of the park.

?

? 4 Remedial measures for frostbite

?

? 4. 1 Remedial measures for minor frostbite

?

? Before figs germinate in early spring, 100 times of multi-effect pesticide can be sprayed to prevent branches from rotting. 7- 10 days after leaf development, a small amount of urea can be sprayed with life essence for 2-3 times. At the same time, reasonable pruning should be carried out according to the freezing injury of branches, and branches with freezing injury symptoms should be cut off. After germination, suitable new branches can be selected and the replacement position can be supplemented by pulling out branches. At this time, we should pay attention to the fact that it is not advisable to cut the branches prematurely in spring, but to prune them when they sprout, taking light pruning as the principle to avoid the branches being drained by the cold in late spring. At the same time, it is necessary to strengthen watering, proper fertilization and integration of water and fertilizer to promote the growth and development of trees.

?

? 4.2 Remedial measures for severe frostbite

?

? If the trunk and branches on the ground of fig have all frozen to death, all the dead branches should be cut off in early spring, and the branches should be re-cultivated by making full use of underground buds. Be careful not to dig trees easily, because under normal circumstances, even if all the above-ground parts freeze to death, the underground parts may not be damaged. In spring, the buds near the roots of fig may germinate, grow strong new branches and form a new crown, but the germination period is a little later than that of normal trees. When selecting buds, all of them can be temporarily reserved, so that the park can recover quickly, so that it can bear fruit in August and September of that year. When it germinates in the next spring, it can leave 3-4 thick and upright main branches, and the others can be removed, which is beneficial to the development and growth of the tree.