Apple rot disease is the most serious disease that damages apple trees in the north. It often causes dead and dead trees.

First, the reasons for the occurrence

1. Blindness, over-reliance on pesticides, and passive hope of the emergence of "specific drugs", resulting in delays in prevention and control.

1 Apple rot disease can not be achieved through the use of drugs to avoid the invasion of bacteria. Conidia of rot disease can germinate at a minimum of 10°C. The germ can germinate except in a few winter weather conditions, resulting in infestation. There is no clear period of infection, and the existing protection agent is usually effective. In 7 to 10 days, the measures to prevent infection by continuous application of a protective agent cannot be implemented in production.

2 apple rot disease can not be achieved through the use of drugs to inhibit the growth of mycelium. The temperature range for the growth of the mycelium of the rot pathogen is from 5°C to 38°C. According to studies conducted by the Changli Fruit Research Institute of the Hebei Academy of Agricultural Sciences, at a temperature of 0°C, the bark temperature on the sunny side can reach 7.7°C, which has exceeded the temperature limit of mycelium growth. When the temperature is 0°C, the germs on the tree have already begun to grow.

Therapeutic agents are mainly benzoylimidazole carbendazim and thiophanate-methyl, which are used to inhibit the formation of spindles during cell mitosis and to prevent the cell division of pathogens, so as to inhibit the growth of pathogenic bacteria and thus avoid crops. The purpose of the disease. Most of the existing bactericides play a role in a specific process in the life activities of pathogens. After use, they can only kill pathogens that are at a corresponding stage of development. The rot of the apple rot is common in orchards, and due to the different temperature and nutritional status of different tissues and parts of the fruit tree, the development level of the rot bacteria is completely inconsistent. Once administered, it can only act on the bacteria that are in the stage of mycelial growth, and it cannot achieve the effect of reducing the bacteria in the fruit tree tissue. The continuous use of drugs within a specific period of time to ensure the presence of drugs in plant tissues for a long period of time is the only way to use therapeutic agents to inhibit the development of germs, but the cost is too high to be realized in production practice.

2. The all-round lack of orchard management in the orchard caused serious rot.

At the present stage, the prevalence of rot in apple trees is nearly 100%, and there are a large number of germs in each fruit tree. However, rot bacteria are limited in their ability to infect and usually only parasitize dead plant tissues. When pathogens come into contact with plant tissues, such as debilitating tree vigor, pathogenic bacteria secrete toxins to kill surrounding plant cells, gain nutrients in dead plant tissues, and further expand outwards, resulting in the death of large barks. Such as strong tree vigor, fruit trees can play a strong inhibitory effect on the bacteria, that is, bacteria difficult to kill the surrounding healthy plant cells, can not obtain nutrients, in a latent state. In this case, despite the presence of a large number of germs, it is difficult to develop. Therefore, whether or not the rot disease is serious is directly related to the tree vigor.

Reasonable fertilizer management is the most effective measure to increase tree vigor. Traditional apple fertilization has always emphasized the principle of "one base and three recovery", that is, a base fertilizer is applied in the fall, three fertilizers are used before the spring sprouting period and the fruit expansion period, and the base fertilizer is mainly farmyard manure and organic manure, according to the principle of "pounding fruit and fertilizer". Apply. Fertilizer is mainly based on chemical fertilizers, in particular increasing the amount of phosphorus and potassium fertilizers. However, in practice, there are many misunderstandings in the following aspects:

1 do not pay attention to the application of base fertilizer. Autumn basal fertilization can enhance the frost resistance of fruit trees in winter and effectively increase the fruit tree vigor in the second year of spring. It can not only effectively improve the quality of flowers and the fruit setting rate, but also can strongly inhibit the occurrence of diseases. However, from the perspective of planting status of various producing areas, most of the fruit growers are lazy to apply organic fertilizers and simply rely on top dressings of fruit trees before germination.

2 single fertilization. Due to the high price of potash fertilizer in recent years, fruit growers generally adopt partial nitrogen fertilizer practices to reduce input costs. The partial application of single components will inevitably cause the lack of other mineral elements in fruit trees, and the partial application of nitrogen fertilizer will often lead to overgrowth of plant tissue, further reducing the content of phosphorus and potassium in fruit trees. According to the existing research, the degree of rot disease is related to the potassium content of bark. The lower the potassium content, the more serious the rot disease is.

3 The location and mode of fertilization are not correct. At present, fruit growers generally apply chemical fertilizers by means of furrows or holes. There are many misunderstandings in specific fertilization positions and application methods. First, the fertilization position is too close to the main trunk of the fruit tree, which severely reduces the exertion of fertilizer efficiency. The level of fertilizer effect depends on the contact area between the fertilizer and the root. That is, the closer the fertilizing position is to the fruit tree, the higher the fertilizer utilization rate. The roots close to the trunk are mostly the main roots without absorption function. The correct fertilization position is under the canopy drip line. Secondly, on the way of fertilization, fruit growers generally adopt the "bread cake type" fertilization method, that is, digging pits, and then put them into fertilizers and then fill in the soil. In this way, the fertilizer exists in the form of a cake in the soil. The root system directly touching the cake will wither and die. The root system growing on the top of the cake cannot absorb fertilizer. Only the root system growing in the lower part of the cake can absorb fertilizer, but this part The root coefficient is limited.

Pancake-type fertilization is not only less effective, but also causes great damage to the normal growth of fruit trees. The first manifestation is the serious occurrence of lobular disease and yellow leaf disease. In recent years, severe leaflets and yellow leaves are common in new branches of fruit trees in northern fruit regions, and traditional methods of zinc supplementation are often ineffective. According to some experts, it is caused by the method of fertilizing cakes. A large number of fertilizers are concentrated on the roots of absorption. On the one hand, a large amount of roots are withered and the absorption function is lost. On the other hand, a large number of fertilizers enter the plant tissue in a short period of time, resulting in too high content of inorganic salts in the catheter, resulting in the loss of water and plant cells in the surrounding tissue, affecting the normal inorganic salt transport. Damage to the transduced tissue directly affects the absorption and supply of nitrogen, which is manifested by the leaflets and yellow leaves of the newborn shoots. More importantly, the damaged tissues can be directly infested and rotted by rot pathogens and aggravate rot disease.

3. Ignore the treatment of wounds.

Ignoring the existence of wounds mainly focuses on two aspects: either the wound is not treated or the wrong treatment is performed, which is not conducive to the healing of the wound.

The rot bacterium mainly infects wounds with dead tissue. Mechanical injury caused by large-scale frostbite and hail, resulting in a large number of dead tissue, is most conducive to the infection of pathogens. Therefore, massive frost damage and hail often cause a pandemic. Large saw cuts are bound to cause a large loss of water. Early studies have confirmed that the lower the water content of the bark, the more serious the rot disease will occur. Bare sawed cuts, especially after the major transformations, are full of tree wounds. If they are not closed, they will be allowed to disperse water, which will inevitably worsen the occurrence of rot disease. Therefore, timely treatment of wounds is very necessary.

For many years, the fruit growers used to continue to use Fumeiqi. Although they have the effect of killing rot bacteria, due to the severe corrosive effect of Fumei, it will greatly damage the formation cells, destroy the callus, and seriously impede wound healing. The use of Formamistat will not only cause new dead plant tissues, but will aggravate the infection of pathogenic bacteria after the disappearance of efficacy, and at the same time hinder the healing of wounds, which is detrimental to the stability of tree vigor.

4. The time of the school was wrong.

An effective clearing of the garden to reduce the number of rot pathogens is an effective means to reduce the amount of rot disease. However, at this stage, fruit growers generally concentrate on the clear parks for rot disease in the spring, which is wrong.

After June each year, fruit trees gradually form a layer of skin, that is, new bark is formed on the fruit trees, and the old bark gradually falls off. The skin is a dead plant tissue, but it also maintains a certain amount of water and nutrients, which is an ideal site for the infection of rot pathogens. If the skin falls off smoothly and burns in the clearing of the clean garden, it will not adversely affect the growth of fruit trees. If the tree vigor is weakened or there is a wound in the periphery, it will remain in the tree for a long time without falling off. After research and observation, after 10 months, the rot pathogenic bacteria will break through the newly formed bark, lurk under the bark, and form brown spots, which will occur when the tree vigor is debilitating.

The growth of rot pathogens does not require a high temperature. In winter, the temperature of the bark on the sunny side of the weak tree is sufficient to meet the growing needs of the bacteria. After germs invade the bark in October, rot germs on some weak trees can attack. The most serious is that there is also a peak of rot in autumn.

The existing clear gardens are all concentrated in the spring, and indeed can effectively eliminate some of the unoccupied germs in the latent state and prevent the bacteria from damaging the fruit trees. However, the bacteria that have already attacked and caused damage have lost their significance.

Second, prevention and control measures

1. Strict autumn base fertilizer.

The nutrients needed for the growth of fruit trees are not the fertilizers that fruit growers apply to fruit trees. Fertilizers that are absorbed by roots of fruit trees must be converted to nutrients required for fruit tree growth through photosynthesis in the leaves. That is, when the leaves have to be present, the fertilizer applied can play its due role. Therefore, the correct autumn fertilization should be carried out one month before the deciduous fruit trees.

In the northern region before October, combined with root fertilization, spraying foliar fertilizer to the leaves, using less rain in September, sufficient sunlight, and a large temperature difference between day and night, supplementing the nutrition of the fruit trees can not only improve the frost resistance of the fruit trees, but also reduce the incidence of rot disease. , It can also improve the quality of flower buds and increase the fruit setting rate.

2. Use the correct fertilization method.

The “three-dimensional” fertilization method is adopted, that is, under the canopy dripping line, more pits are digged, and less fertilizer is used to increase the contact area between the fertilizer and the root system and improve the fertilizer efficiency. When digging pits, the excavated soil is conically stacked on one side of the pit. Fertilizer is then sprinkled on the surface of the mound. Starting from the side of the mound, the soil is gradually filled into the pit. In the process of filling, a homogeneous mixture of soil and fertilizer has actually been achieved without adversely affecting the root absorption.

3. Take the correct fertilizer ratio.

The ratio of nitrogen, phosphorus and potassium required for normal growth of apple trees is 2:1:2. This ratio reduces the supply of nitrogen fertilizer, enhances the supply of potassium fertilizer, and improves the ability of fruit trees to resist spreading of rot disease spots.

4. Properly handle tree wounds.

At this stage, the emphasis on the treatment of wounds is not to prevent pathogens from infecting them by means of drugs. The significance of this is to remove dead tissue around the wound and to avoid the loss of water from the tree. Since rot bacteria can only infect wounds with dead tissue, after the disaster such as hail, timely removal of dead tissue on the surface of the tree, scraping off large areas of dead skin caused by freezing is an effective way to prevent infection and attack of bacteria. means.

For large saw cuts, be sure to use paint or plastic wrap. For wounds, do not use corrosive Familia. According to Professor Shi Chunxi of the College of Plant Protection of Northwest Agriculture and Forestry University, triazole bactericides and antibiotic-type bactericides can promote the formation of plant callus and are beneficial to wound healing.

5. Clear clear park time.

The clear garden time for rot disease should be concentrated around October. The first step is to scrape as far as possible the skin layer that has not yet fallen off, so as to prevent the rot bacteria on the skin layer from penetrating the cortex and lurk under the bark formation layer to form subcutaneous dry spots. Followed by the eradication of these newly invaded cortex, has not yet developed rot disease. Therefore, at this stage, the clear garden of rot disease should be carried out before the peak of rot disease in autumn in October.

6. Choose the right medicine.

The use of pesticides to prevent most diseases aims to prevent the infestation of pathogens or to inhibit the growth of newly infected pathogens. However, due to the special nature of rot disease, the use of rot disease should be aimed at eradicating the infected bacteria. Therefore, the drug must be selected from the eradicator. According to years of research, the use of Difenoconazole to take "two spray two brush" measures can effectively reduce the incidence of rot disease. Such as 10% difenoconazole water dispersible granules, before the budding of the fruit trees and after the deciduous, the whole park spray 5000 times liquid; in June to July, once a month 10% difenoconazole water dispersible granules 1,000 times liquid application of large branches of fruit trees, big stems. After the rot spots were found, the lesions were properly scraped off, and in particular, attention was paid to scraping until the bark appeared yellow-green, and the edges of the scrapes were neat, and then the 5% caprozoleol microemulsion was applied 300 times. This kind of measures against rot disease also has special effects on the control of Thunb.

7. Treatment of the root system.

According to the results of the study, early spring through the method of covering the plastic film on the tree disk, increase the ground temperature and promote the early development of the root system can effectively reduce the incidence of spring rot disease.

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