Types and Control Measures of Apple Diseases

Abstract: Due to climatic conditions and unscientific management, apple trees will have different types of diseases, which affect the yield and quality of apples to a certain extent. By analyzing the causes and regularities of different diseases, targeted prevention and control measures can be taken to improve the effect of disease prevention and control.

1. Canker disease

1.1 The cause of the disease

1.1.1 Unstable soil moisture content

In winter, apple trees will suffer from freezing damage due to insufficient water and nutrient supply, resulting in the occurrence of canker disease. If there is a flood, the apple tree will also have fallen leaves and rotten roots, and even die.

1.1.2 Improper fertilization

Insufficient or excess nutrients during the growth process will affect the growth of apple trees and lead to the occurrence of canker disease. In addition, improper fertilization will affect the absorption of nutrients by apple trees and increase the probability of apple tree canker disease.

1.1.3 Unprotected pruning wounds

Apple tree pruning wounds are not protected from the sun and rain for a long time, which will not only increase the probability of canker disease, but also lose a lot of nutrients and water, resulting in the wound not healing normally.

1.1.4 Damage caused by pests and diseases

The fallen leaves of apple trees under the influence of drought and high temperature will breed a large number of pests, which will cause great harm to the leaves of fruit trees, at the same time, powdery mildew is prone to occur, which can easily increase the probability of occurrence of canker disease.

1.1.5 Improper response to frost damage

Excessive application of nitrogen fertilizer to apple trees during overwintering will lead to leggy growth of apple trees, which is not conducive to nutrient storage. During overwintering, it is easy to suffer from freezing damage and increase the probability of canker disease.

1.2 Comprehensive control measures

1.2.1 Cultivation management

Do a good job in the cultivation and management of apple orchards to improve the ability of fruit trees to resist disease. The field cultivation and management methods mainly include fertilization, irrigation, and garden hygiene.

1.2.2 Physical control technology

Choose physical control techniques according to the characteristics of the latent infection of pathogenic bacteria, including paste mud method, expansion and scraping method, and disease scar bridging method.

1.2.3 Chemical control

Chemical control is the main method to control apple tree canker disease. Lime sulfur mixture, copper sulfate solution and sodium humate are all traditional effective medicines.

1.2.4 Biological control

The first is antibiotic control. Antibiotic control can reflect the characteristics of high efficiency and low toxicity, and can promote the healing of scars. The common antibiotics are fermentation broth. Relevant studies have shown that the cure rate of fermentation broth in preventing and treating canker disease can reach 100%, At the same time, it can promote the healing of the surrounding tissue and have a bactericidal effect. The second way is control it through botanical pesticides. The study found that ozone oil has obvious effect on the prevention and treatment of apple tree canker disease, after 120 days of cure, the recovery rate can reach 97%, and the recurrence rate is low.

2. Ring rot disease

2.1 The cause of the disease

2.1.1 Climatic conditions

Rainy weather will increase the probability of occurrence of Ring rot disease. Rain conditions are required for the dissemination and infection of pathogen spores. If the precipitation is more than 10mm, the latent bacteria will distribute spores around, and the pathogen spores will adhere to the surface of the fruit, thereby infecting.

2.1.2 Improper control measures

If the infected branches and rotten leaves are not cleaned up in time, it will lead to the spread of the ring rot fungus.

2.2 Comprehensive control measures

2.2.1 Strengthen field management

After the fruit is harvested, the dead branches and diseased leaves in the orchard should be thoroughly cleaned up and buried or burned. Before fruit trees sprout, the diseased spots should be scraped off in time, and 50 times of 5% fungus clear solution should be applied. Timely pruning and thinning, scientific fertilization, appropriate application of organic fertilizers and foliar fertilizers to improve disease resistance of fruit trees.

2.2.2 Chemical control

First, the critical period for the prevention and control of ring rot disease is before the germination of fruit trees, and 8% ring rot clean 100 times liquid can be selected for spray control. Second, every summer, the orchard is in a high temperature and high humidity environment, which is a period of high incidence of wheel striae. During this period, drug spraying should be strengthened. It can be controlled by spraying 200 times of Bordeaux mixture or 800 times of 70% thiophanate-methyl powder. Third, bagging the fruit. Spray the fruit about 50 days after the fruit tree blooms. When the liquid is completely dry, bag the fruit and seal the bag in time. The bag should be removed about 30 days before the apple is picked.

3. Leaf spot disease

3.1 The cause of the disease

3.1.1 Climatic reasons

Spotted leaf leaf disease is prone to occur when it is hot and rainy, and the disease occurrence period is delayed when it is dry. In summer, there is more precipitation and the disease is more serious.

3.1.2 Reasons for fruit tree varieties

Among all apple varieties, the delicious line is very susceptible to disease, and the Fuji line is less susceptible. Poor ventilation and light transmission in apple orchards, weak trees and low-lying terrain will also increase the probability of disease.

3.2 Comprehensive control measures

3.2.1 Agricultural control

1) Choose varieties with strong disease resistance.

2) Thoroughly clean up the fallen leaves in the orchard, and take them out of the orchard for deep burial or incineration.

3) Destroy the conditions for the reproduction of germs, promote thinning and pruning techniques, improve the ventilation and light transmittance of apple orchards, and prevent the emergence of germ spores.

4) Scientific fertilization, increase the application of organic fertilizers, nitrogen fertilizers and potassium fertilizers, and do a good job in autumn fertilization. The amount of fertilizer applied in autumn should account for 60% to 70% of the annual fertilization amount, and the amount of nitrogen fertilizer and potassium fertilizer should be well matched to avoid partial application of nitrogen fertilizer and phosphorus fertilizer. 

5) Do a good job of bagging apples, and insist on using triazole fungicides for control after rain.

3.2.2 Chemical control

1) Spray fungicides immediately after the disease is found, and different fungicides should be used alternately. Alternative biocides include bordeaux mixture and systemic biocides.

2) Reasonable planning of spraying time and scientific spraying. Use good physical and chemical spray equipment, combined with the law of disease occurrence, spray evenly.

4. Brown spot disease

4.1 Causes of the disease

Apple brown spot is a fungal disease. The pathogen overwinter in the diseased leaves. In the second year, a large number of fungal spores will be produced, which will then be spread by wind and rain and directly infect the leaves. The lower part of the tree crown is easy to get sick, and then it spreads to the upper part, and the incubation period is relatively long, usually 6 to 12 days.

4.2 Comprehensive control measures

4.2.1 Cleaning in the park

After the leaves of the apple tree fall in autumn and before germination in the following spring, thoroughly remove the diseased leaves and weeds in the orchard. Before the apple germinates, the land should be ploughed to promote the decomposition of the leaves. Do a good job in shaping and pruning branches, and clean up diseased branches and fruit in time.

4.2.2 Water and Fertilizer Management

Apply fertilizer scientifically according to the nutrient requirements of apple trees, increase organic fertilizer appropriately, and adjust the ratio of nitrogen, phosphorus and potassium. From the budding stage to the tipping stage of apples, high nitrogen formula fertilizer can be selected. During the flowering and fruit setting period, it is necessary to control the application amount of nitrogen fertilizer. From the expansion period of apples to the maturity and coloring period, high-potassium formula fertilizer can be used.

4.2.3 Scientific pruning

Adjust the tree load according to the soil fertility conditions and the characteristics of the variety to ensure the healthy growth of the apple tree and control the number of fruiting branches. Scientific pruning to ensure ventilation and light transmission. Typically, pruning is done 2-3 times a year.

4.2.4 Chemical control technology

Control the spraying time and frequency, and adhere to the principles of more rain more spray and less rain less spray. In rainy years, it can be added 1-2 times appropriately. For seriously ill orchards, drug spraying can be carried out 10 days before the onset of the disease, focusing on the leaves in the middle and lower parts of the apple tree and the leaves in the inner tree crown of the tree.

5. Conclusion

Apple trees will encounter various types of diseases in the process of growth. The above-mentioned four representative diseases of apple trees are the main points, and specific control measures are put forward on the causes and symptoms of apple tree diseases. However, in the face of global due to the variety of apples and regional differences, the above control measures cannot cover all apple diseases. We hope to inspire more control methods and promote the further development of apple planting.