When the temperature drops and the weather is cold, the requirements for citrus farming are very high. In order to reduce the citrus losses caused by freezing and frost weather disasters, it is recommended to take certain preventive measures in time for frost-prone orchards. The editor has compiled some prevention measures Let’s take a look at the methods of freezing damage.

Frost Disaster Characteristics

The degree of frost damage in winter depends greatly on the orchard’s geographical location, topography, variety, extreme low temperature, low temperature duration, and the magnitude and speed of temperature rise after the cold wave. Big difference.

1. Orchard terrain. Slope foot orchards, flat land orchards, depression orchards and basin orchards are severely affected, while sloping land orchards and high slope orchards are less affected.

2. Altitude

For the same tree species and in the same location, the frost damage in high-altitude orchards is more severe than in low-altitude orchards. Under the same longitude conditions, the degree of low-temperature frost increases with altitude.

3. Varieties

In the same orchard with the same terrain, grapefruit and citrus are heavier, tangerines and tangerines are lighter, early-ripening and medium-ripening Wenzhou mandarins, navel oranges, Nanfeng mandarins and The degree of frost damage in Pengkan is basically the same. Shatian honey pomelo is less affected, honey pomelo is more affected, sugar orange, fertile orange and Ma Shui orange are more affected, and summer orange is less affected.

4. Tree age and organs

Adult trees suffer less damage, while seedlings suffer more; old and mature shoots suffer less damage, while young shoots suffer more damage. Flower organs are more damaged, fruits are more damaged, and branches and leaves are less damaged. The damage to the top of the crown is more severe than that of the middle and lower parts. Autumn shoot leaves were seriously damaged, while summer shoots and old leaves were slightly damaged.

Characteristics of frost damage at different low temperatures

When the temperature is 0℃, immature leaves curl and buds turn brown due to frostbite - at 1℃, autumn leaves begin to Curling, the edges and backs of the autumn leaves of non-frost resistant varieties turn brown due to frostbite and then curl. The tops of the young shoots are frostbitten, brown and dry - at 2.0°C, the autumn shoot leaves of sweet orange, summer orange, grapefruit and banana orange are frostbitten, curled and withered. In severe cases, they will fall off their leaves and the autumn shoot tops will be frozen to death. And drying - at 3.0℃, overwintering fruits, especially summer oranges, sugar oranges, fertile oranges, banana oranges, Maogu oranges, horse water oranges and kumquats, are damaged by freezing. After the snow melts, the fruit loses water and shrinks, the sap is crispy and shrinks, and the sap is less and tasteless. At 4.0°C, the bark of the trunk cracks, especially the cortex of 1-2 year old saplings. Kumquat fruits are severely damaged by frost and will suffer severe fruit cracking and fruit drop.

Measures to prevent and control low-temperature frost disasters

1. Pay attention to weather forecasts in a timely manner and do a good job in preventing cold wave weather disasters.

Let’s continue to introduce the topic of this issue in depth.

2. Collect, store or sell fruits in time before frost.

3. Before the frost arrives, overwintering fruit varieties such as kumquats, sugar oranges, fertile oranges, horse water oranges, late-ripening banana oranges, hairy bone oranges, and summer oranges can be covered directly or under an arch above the canopy. Plastic film to reduce or avoid frost damage; for trees that do not bear fruit, you can use grass to tie the trunk or cover the crown and flower disk to reduce frost damage.

4. Smoking in the orchard before frost can reduce frost losses.

5. The suitcase is painted white. The whitening agent is prepared according to the ratio of quicklime: sulfur powder: salt: water: 1:0.1:0.07:3 and a small amount of edible oil. Before frost comes, apply a whitening agent evenly under the main trunk of the tree, or directly spray a commercially available whitening agent to reduce freezing damage and the damage of overwintering pests.

Post-disaster management suggestions

In order to reduce anthracnose and resin diseases caused by frost disasters, avoid further withering of affected branches, and minimize losses, orchards damaged by frost should be damaged according to the Take corresponding technical measures to the extent:

1. Protect old leaves and prevent defoliation caused by frostbite. When the post-disaster temperature rises above 12°C, a variety of elemental foliar fertilizers can be sprayed, such as 1200 to 1500 times of brassinolate solution, 0.4% compound fertilizer solution, etc.

2. Because of pruning trees. After freezing, when the temperature stabilizes at 12~15°C in the second spring, pruning will be carried out according to the degree of frostbite and winter and spring pruning conditions.

(1) For immature autumn shoots that are slightly frozen, partially withered or defoliated, thinner immature autumn shoots can be cut from the base.

Mature tips around the crown with the same degree of damage can be combined with spring pruning, and short or partial thinning can be carried out 15 to 20 days before the emergence of spring tips;

(2) Severe defoliation after freezing Branches and twigs can be retracted or cut directly from the top of the base branches with leaves and full buds.

(3) For trees whose spring shoots and flower buds are severely frostbitten due to spring frost, the autumn shoots, summer shoots or spring shoots of the previous year should be re-cut to promote the robust growth of their late spring or early summer shoots. , restore the vitality of trees.

(4) Trees that have slight frostbite on their spring bamboo shoots and flower buds but still have a certain number of flowers should be pruned, mainly to protect the fruits. On the basis of spraying to prevent anthracnose and resin disease, the autumn bamboo shoots below the frostbitten spring bamboo shoots should be appropriately shortened to promote healthy new shoots. At the same time, properly drain some dense twigs that are not damaged by frost to increase the fruit setting rate.

3. Apply quick-acting fertilizers in a timely manner to ensure nutrient supply. Mainly use water and fertilizer. Before pruning, you can spray and rinse fertilization, manure water or rotten bran water containing nitrogen, phosphorus, potassium and medium and trace elements 1 to 2 times.

4. Carry out targeted pest and disease control. Diseases such as anthrax and resinosis are prone to occur after freezing. Therefore, spray pesticides promptly after freezing to prevent anthrax, resinosis and other diseases. 80% Dasheng m-45 wettable powder 500 to 800 times, 25% prochloraz 800 to 1000 times, 25% phenanthrozole 2500 to 3000 times can effectively control anthrax; 80% mancozeb wettable powder 600 times, 25 % pyraclostrobin suspension 1000~1500 times and 80% Catan water dispersible granules 1000~1500 times can control resinosis. Sprays can be applied together with foliar fertilizers.

5. In recent years, due to the low prices of fruits, especially sugar oranges, some orchards that are severely frozen and have no harvest may relax or even give up management. For these orchards, we should be alert to outbreaks of citrus psyllid and Huanglongbing, which threaten the survival of nearby orchards. Therefore, the joint prevention and control of citrus psyllid and Huanglongbing should be strengthened after the disaster.

Through our introduction, I believe that everyone has a deeper understanding of the prevention measures for citrus frost damage and how to prevent and treat frost damage in citrus. Hualiuba will be constantly updated. If you like us, remember to bookmark it and share it by the way.