How to prevent frost damage in plum trees? Key technical points for frost prevention when growing plum trees

Frost injury and freeze damage refer to the phenomenon in which the soil and plant surface temperatures drop to 0°C or below 0°C for a short time at night during the growing season, or when frost occurs, causing damage to the young and tender parts of fruit trees. In China, the average annual area affected by frost damage reaches 340,000 km2, and in the worst year it reached 770,000 km2, causing annual losses of 3 billion yuan to crops, fruit trees and vegetables. In particular, in recent years, late frost damage has been especially severe in northern China. Some fruit trees that bloom early in spring often suffer from late frost, with light cases reducing yield and severe cases causing total crop failure. In some areas, late frost damage has become a limiting factor for the development of fruit growing.

In order to effectively prevent late frost damage in the future, here are a few suggestions for you and other friends for reference:

I. Relationship between orchard terrain and freeze damage

According to surveys of freeze-damaged fruit trees in Qixia, Penglai, Zhaoyuan, Laiyang, Haiyang, and Muping counties and cities (districts), the severity of late frost damage is related to orchard site conditions and terrain. Because water has a large heat capacity, it absorbs a large amount of heat during the day and releases it at night, thereby slowing the impact of drastic temperature changes. Therefore, fruit trees within about 10 km of the coast and around water sources suffer lighter freeze damage, followed by orchards at mountain tops and wind gaps with greater airflow and frequent gas exchange, and orchards at higher elevations suffer lighter damage. The most severely damaged are flat lake lands, dried-up riverbeds, and low-lying flat land, because cold air accumulates in low-lying areas. In the survey, it was found that in orchard plots that suffered total crop failure from freezing, branches above water pools and pesticide pools had an extremely high fruit-setting rate, with almost no impact on yield. In the same orchard, plots with weak tree vigor suffered heavier freeze damage than plots with strong tree vigor. Sandy beach orchards suffered severe damage, while orchards on clay soil suffered relatively lighter damage.

II. Relationship between tree rows and freeze damage

For fruit trees such as apple, pear, and apricot, the lower part of the canopy is more severely affected and the upper part less so. According to survey results in Qixia, Penglai, Longkou, and Zhaoyuan, severe freezing of flowers and fruits was mainly concentrated below 1.6 m from the ground, while above 2 m there was basically no freezing damage. Peach trees with natural open-center form suffered severe freeze damage, while spindle form suffered lighter damage. Young peach trees had severe freeze damage to young fruit in the inner canopy and lower part, while young fruit in the upper part of the tree suffered lighter freeze damage. Mature peach trees had lighter freeze damage to young fruit in the inner canopy and lower part, while young fruit in the upper part of the tree suffered heavier freeze damage.

III. Management measures and late frost damage

Through large-scale trial and demonstration surveys, it was found that under the same site conditions, orchards showed different degrees of damage and different tree vigor due to different management levels, and the degree of damage varied greatly. After using “Tianda-2116”, first, it showed cold resistance and frost protection, with a high germination rate of frozen branches and buds, and an obvious cold-resistant and frost-preventive effect. Second, the fruit-setting rate was high, fruit setting was uniform and consistent, the fruit stalk was long, and the fruit cluster was long, about one third larger than fruit clusters and fruit stalks that had not been sprayed. The survey found that orchard plots irrigated with winter freezing water before the New Year and with pre-bloom water in spring, and therefore with relatively high soil moisture, suffered lighter damage, while plots without winter freezing water and pre-bloom water suffered heavier damage.

IV. Remedial measures after fruit tree freeze damage

In order to minimize the losses caused by frost to fruit tree production, and in combination with the specific conditions of damage to different fruit trees, a series of targeted preventive and remedial measures are proposed:

1. Use science and technology to avoid freeze damage

The harm of freeze damage to plants is mainly that, on the one hand, it destroys the membrane structure in cells, and on the other hand, the destruction of the membrane causes metabolic disorders. Because the concentration of the aqueous solution in the intercellular spaces is lower than that of the cell sap, water in the cells leaks outward. After spraying “Tianda-2116”, the leakage of cytoplasmic fluid can be effectively reduced, moisture can be maintained, and the cells can be protected. Even if freeze damage occurs, the cell membrane system can be repaired in time, thereby achieving the purpose of preventing freeze damage. Practice has proved that “Tianda-2116” plant cell membrane stabilizer, a key product promoted under the national “863 Program”, can effectively resist the damage of adverse factors such as freezing. Applying “Tianda-2116” to the trunk can better promote the growth of damaged fruit trees and reduce losses caused by freeze damage. In addition, while using science and technology, the first thing is to choose a good orchard site. Generally, low-lying land and closed valleys easily accumulate cold air and are prone to freeze damage; while planting trees on hills, sunny slopes, and around reservoirs allows air circulation and lowers the probability of freeze damage.

2. Irrigation

Irrigation or sprinkler irrigation when spring growth begins can significantly lower soil temperature and delay germination; after germination and before flowering, irrigating another 1-2 times can generally delay flowering by 2-3 days. Irrigation or sprinkler irrigation before freeze damage can also increase soil temperature and tree temperature, and can prevent and reduce freeze damage.

3. Whitewashing

Whitewashing the tree body in early spring can effectively prevent sunscald and can delay germination and flowering by 3-5 days. Whitewashing can not only prevent freezing but also effectively control pests and diseases. (Formula: quicklime 10 parts, salt 1-2 parts, flour 35-40 parts)

Using the above two measures can delay the flowering period by 5-7 days. After all, flowers and flower buds have a significantly stronger ability to resist freeze damage than young fruit.

4. Strengthen management and build strong tree vigor

Frost causes varying degrees of damage to young fruit, new shoots, and leaves of fruit trees. In order to restore tree vigor as soon as possible, fertilizer and water management should be strengthened, tree nutrition should be supplemented, the cell sap concentration of the fruit should be increased, and the drought resistance and disease resistance of the tree should be enhanced. Apply more fertilizer before and after flowering, apply compound fertilizers such as special fertilizer for fruit trees as a top dressing, and spray “Tianda-2116” in coordination. Spray 600 times dilution of “Tianda-2116” once every seven days for repair and remediation, spraying twice in succession, to restore tree vigor, increase the fruit-setting rate and single fruit weight, and ensure a good harvest in a disaster year. In particular, do a good job of foliar fertilization. Choose high-quality liquid fertilizers, such as 0.3% potassium dihydrogen phosphate solution or 0.3-0.5 urea solution.

5. Chemical protection

After the tree body is frozen, tree vigor is weaker and disease resistance is reduced, making it highly susceptible to pest and disease damage. Timely spray thiophanate-methyl, polyoxin, triadimefon, or carbendazim, etc., to prevent and control infection by pathogens such as powdery mildew and Alternaria leaf spot and damage by pests. You can also spray protective chemicals on the afternoon or evening of the day the freeze damage arrives. For example, “Tianda-2116” contains a large amount of molecular chain active substances. After spraying, it forms a molecular film on the surface of the tree body, and its various trace elements can increase the concentration of cytoplasm. It can effectively activate chitinase and protease in the crop, greatly increase the content of amino acids and chitin, increase the content of unsaturated fatty acids in cell membranes, lower the freezing point of cells, and enable normal growth at low temperatures.

6. Reasonable pruning and heading back

For all trees and varieties, do not rush to prune or remove damaged branches, leaves, and fruit in the short term. Instead, adopt the method of late fruit thinning and leaving more fruit, retain fruit that is undamaged or only lightly damaged, and ensure more fruit and good fruit to make up for the losses caused by frost. At the same time, branches of the tree body should be spread and angles opened to control vegetative growth and allow natural recovery. In mid-May, branches that were damaged by frost and cannot recover should be promptly cut off or headed back to healthy parts to promote new sprouting and branching; frozen branches and buds should be wiped off to promote latent buds to bear fruit and make up for the shortage in yield. For orchard plots of old and inferior varieties that suffered total crop failure, spring hardwood grafting or green shoot grafting can be used to replace them with famous and superior varieties. Do a good job of pruning during the orchard growing season, regulate nutrient distribution, and ensure the needs of fruit growth and development and flower bud formation.

7. Producing smoke

Smoking is a common method used by fruit growers to deal with freeze damage. The preventive effect depends on the quality of the smoke produced. In high-quality orchards, the temperature is about 2°C. There should be at least 5-6 smoke piles per mu, evenly distributed in all directions. The grass pile should be 1.5 m high and 1.5-1.7 m in base diameter. When stacking grass, insert several thick wooden rollers vertically and diagonally, and after stacking, pull them out to make ventilation holes. Place flammable materials into the interior of the grass pile through the holes, and cover the outside of the grass pile with a layer of wet grass or wet mud. In this way, the amount of smoke is sufficient and the duration is long. Smoke-producing materials can use crop straw, weeds, fallen leaves, and other flammable materials that can produce large amounts of smoke. Smoking has a certain effect on slight freeze damage above -2°C, but if it is below -2°C, the preventive effect is not obvious.

Nowadays, in some places environmental damage is severe and various natural disasters occur frequently, so fruit growers cannot be careless. They should prepare for a rainy day, watch the weather forecast every day, and make emergency preparations in advance. No matter how much is said, strong tree vigor naturally gives a stronger ability to resist freeze damage, just as people with strong physiques resist cold while weak people fear cold. However, if the temperature is really low, the effects of the above methods will all be unsatisfactory.