Golden Delicious Apple is a major producer in Europe and America. It has high yield and stable production, large fruit quality, and strong adaptability. In China, there is also considerable cultivation area and production. However, in most production areas, especially in the cold and humid regions of the coastal areas and young fruit, the occurrence of fruit rust is widespread. Severe rust spots are contiguous and the fruit surface is rough, which greatly reduces the commercial value of the fruit and its development is limited. The causes and prevention methods are summarized below for reference. 1 Causes of Rust Fruit rust is a physiological disease that occurs on the surface of the fruit of Golden Delicious. Its main manifestation is the rusting of wood on the fruit surface. The occurrence of the disease is the result of a combination of internal and external factors. Intrinsic factors mainly refer to the fruit structure of Golden Delicious apples that favor the formation of fruit rust. External factors mainly refer to the impact of spraying, adverse weather conditions and other factors. 1.1 Intrinsic factors The occurrence of fruit rust in Golden Delicious apples is closely related to the structure of its peel. The epidermis cells of Golden Delicious apple fruit are large and thin, with many gaps, loose arrangement, large epithelial cells, loose arrangement and neatness, and prominent lenticels in the lenticels. The spherical complement cells are loosely arranged. This characteristic of Golden Delicious apple skin makes it vulnerable to damage and creates favorable conditions for the formation of fruit rust. Once adverse external factors are affected, the stratum corneum ruptures and it is very easy to cause puncture and other weak links to rupture, resulting in corkation. The formation of fruit rust. The underdevelopment of the stratum corneum and weak protection of the fruit are another important internal cause of rust in the fruit peel of Golden Delicious apple. The cuticle of the fruit of Golden Delicious apple is very thin, with no flaky crystals, uneven coverage, loose attachment, easy breakage and cracking, resulting in bare skin cells, stimulated by undesirable external factors such as moisture and liquid medicine, bare epidermal cells and Some of the epithelial cells will be corked and the results are rusted. The occurrence of fruit rust in Golden Delicious apples is also related to the nutritional level. The higher the fruit's nutritional level, the stronger its resistance to adverse environments. The study found that the contents of nitrogen, phosphorus, and potassium in peels and pulps were rustless> light rust> medium rust> heavy rust. However, there are also literatures that high nitrogen content in the tree will promote the increase of cell volume and lead to increased fruit rust. The relationship between soil nutrients and fruit rust and the level of nutrients is similar, but its effect on the occurrence of fruit rust is indirect, and it is manifested by affecting the fruit's nutritional level. In addition, the number of fruits on the table will also affect the occurrence of fruit rust. The more fruits on the table, the more fruit rust will occur. Tests have shown that leaving three fruits is more important than leaving double fruits, and leaving double fruits is more important than leaving single fruits. The reason for this is that the remaining fruit is prone to nutrient competition, resulting in insufficient nutrition of the fruit and poor growth and development. In addition, hormonal imbalances are also one of the causes of increased fruit rust. 1.2 external factors on the external factors causing fruit rust, the relevant literature will be summarized as flowering or young fruit early frost or near frost, fruit early development stage of rain, high humidity, condensation, especially after dew condensation Strong sun exposure, canopy rain, dew and drip, etc. dry slowly, sun exposure, phytotoxicity (when the weather conditions are conducive to rust, most chemicals, even water can be gathered into rust), young fruit by machinery Injury, Rust ring virus, Powdery mildew, Fungus and other 13 species. Among the many external causes of fruit rust, pesticide spraying and adverse climatic conditions are the two most important factors. Many pesticides, such as Bordeaux's liquid, lime sulfur and other alkaline agents, parathion, omethoate, methamidophos, and mercury preparations, will increase the occurrence of fruit rust in young fruit spray. For example, water-soluble copper sulphate in Bordeaux mixture invades stomata or epidermal cells, promotes the formation of stomatal and epidermal cells and becomes cork tissue. Mercury in mercury preparations affects the enzymatic reaction and inhibits the stratum corneum. Keratin formation. In addition, spraying operation technology will also affect the occurrence of fruit rust in Golden Delicious apples. Only choose the appropriate spray aperture, spray pressure, nozzle and fruit distance, will not cause fruit surface damage, avoid fruit rust. The rain can directly stimulate the peel. After the rain enters the peel through the cuticle of the stratum corneum, the epidermis and the epithelial cells are easily broken due to the increased pressure and cause rust. The influence of meteorological factors on the occurrence of fruit rust in Golden Delicious apples is mainly achieved by influencing the attachment time of moisture on the peel. Studies have shown that, among the meteorological factors in the sensitive period of fruit rust occurrence, the relationship between rainfall and fruit rust is not obvious, and the temperature, relative humidity of the air, and the rainfall day are crucial to the occurrence of fruit rust, and the number of rain days is the most critical. The number of rainfall days is long, the fruit surface is long for water, and fruit rust is heavy. After the rain or after the spraying, the low temperature and high humidity are not conducive to evaporation of water and will prolong the time for fruit surface watering, and high humidity conditions will also hinder the formation of fruit wax, which is beneficial to the formation of corks. 2 The sensitive period of the occurrence of fruit rust in Golden Delicious apples is generally 15 to 40 days after flowering, and the most sensitive period of rust is about 25 days after flowering. Therefore, the prevention and control of the fruit rust of Golden Delicious apples should be carried out before this. 2.1 Fruit Bagging Fruit bagging is an effective method to prevent fruit rust in Golden Delicious apples, which can basically guarantee fruit rust, or greatly reduce fruit rust. The non-rust fruit rate is generally above 90% and the highest is up to 100%. If the fungicide is sprayed before bagging, the effect of preventing fruit rust will be better. There are two main reasons for fruit bagging to increase the rust-free fruit rate. One is to protect fruits from adverse environmental effects, and the other is to promote fruit wax formation and thickening of the stratum corneum and enhance fruit self-protection. The fruit bagging has low cost and high efficiency, and is suitable for promotion in a large area. However, it should be noted that bagging must be carried out immediately after flowering, and should be completed before the arrival of cold and humid weather, and only one fruit per fruit bag can be set. 2.2 Spraying fruit rust inhibitors such as carbendazim, thiophanate-methyl, carbendazim gel suspension, anti-rust spirits and paraffin emulsifiers, etc. have good anti-rust effect and no rust-proof rate. It is 25% to 76% higher than the control (without spraying any fruit rust inhibitor, the same below). Among them, the rust preventive effect was the best. After spraying for 12 days, 30 days, and 45 days, the rust-proofing agent was sprayed 500 times each time. The 5-year average good preserved fruit was as high as 93.8%, while the control was only 17.4%. The control effect of the drug on spotted leaf disease is also extremely significant, and the good leaf rate can reach 96.5%. It has also been reported that in combination with the control of other pests and diseases, zinc-copper Bordeaux liquid (zinc sulfate 0.5. copper sulfate 0.5, quicklime 2, water 100) or zinc sulfate lime liquor (zinc sulfate 0.5, quicklime 1, water 100 ) Replacement of Bordeaux mixture can reduce the harm to young fruit. When the air humidity is too high during the young fruit period, spray 100 times lime milk 1 to 2 times to increase the hygroscopicity of fruit surface and reduce the occurrence of fruit rust. In areas with extremely rust-prone conditions and in orchards with heavy fruit rust in past years, the plant growth regulator ca4+7 can be sprayed from the beginning of flowering and sprayed once every 10 days for a total of 4 injections; it can also be sprayed before and after the onset of disease. - 2 times 40% carbendazim 600 times. Sprinkle before the lime sulfur mixture, sulfur, captan, myclobutanil, Le Bigen and other fungicides can also reduce the occurrence of fruit rust. In addition, the atomization process should be as high as possible during the spray of the medicament to reduce the amount of sticking of the medicament on the fruit surface. 2-3 Strengthen cultivation management Strengthen orchard soil management in orchards, prevent soil water accumulation, increase organic fertilizers, and increase phosphorus and potassium fertilizers. Strengthen the tree vigor, improve the nutrient level of the tree, and do a good job of pruning. Prevent the closure of orchards and improve ventilation in orchards; carry out artificial pollination, bee or wall bee pollination to ensure adequate fertilization; strict sparse fruiting and fruiting, reasonable load (as far as possible to retain single fruit), promote fruit development, and enhance adverse effects on external environment The resistance; in the rapid expansion of the fruit, in case of drought, should be appropriate irrigation; In addition, should also be avoided as far as possible spraying rust-prone chemical agents.
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