In recent years, the vigorous development of kiwifruit has become the leading industry for increasing farmers' income. However, with the extension of the planting period, coupled with unscientific management, it will easily lead to the widespread occurrence of yellowing disease, which will increase year by year, and it will be difficult to prevent and cure. This will seriously affect the quality, yield and commodity rate of kiwifruit. In the prevention and treatment of the disease, it is necessary to distinguish the cause of the disease and apply the disease.
Why do fruit trees have yellowing disease
During the growth period of fruit trees, the leaves appear chlorotic yellow, and when severe, they die. This phenomenon is called yellowing disease. Yellowing leads to a decrease in photosynthesis capacity, which affects fruit production and quality. The causes of yellowing in fruit trees are as follows:
Invasion of pathogens and pathogens through the invasion of pathogens, viruses, and mycoplasma and other pathogens causes destruction of the root tissue and leaf tissue of fruit trees, such as root rot, root and stem blight, etc., which are the most common and serious due to various The secretions can clog the delivery system so that they cannot absorb water and nutrients. The raw materials necessary for photosynthesis are not supplied, and the leaves appear green and yellow.
Changes in Natural Conditions Changes in natural conditions, such as temperature, moisture, and air, can affect the growth of fruit trees. When the temperature is too low, the soil nutrients are not easily activated or released, and the crop is difficult to absorb; the temperature is too high, the transpiration of the leaf surface and the evaporation intensity of the ground are increased, resulting in excessive water loss in the soil, the crop is not supplied with sufficient moisture, and the soil moisture is too low. Soil nutrients can't move with water for poor crop absorption. Excessive water can cause significant reduction of soil air, resulting in anoxic conditions that affect root respiration. These changes in natural conditions can all obstruct the absorption and utilization of nutrients, moisture, and gases in the roots, resulting in chlorosis and yellowing of the leaves.
Soil nutrients Soil nutrients are the most direct and sensitive factors causing yellowing of fruit trees. There are many types of nutrients that cause yellowing of fruit trees, such as nitrogen, potassium, magnesium, boron, iron and other elements, which can cause yellowing of the leaves. Farmers can use special fertilizers with different functions to cure and prevent the adverse effects caused by lack of ingredients. However, the lack of iron can not be solved by general fertilization. Because the degeneration of iron is too large, it is difficult to maintain the effective state of iron. Therefore, iron has to be supplemented in many ways. (Encyclopedia)
Kiwifruit growing season yellowing disease
Kiwifruit growing season more frequent and related to the following factors:
Varieties of different varieties of yellowing disease incidence and incidence of a large difference, with the most serious disease of Qinmei varieties, followed by Xu Xiang, Jin Xiang, Hayward, Hongyang incidence is lighter.
When the pH value of the soil is slightly alkaline, the ferrous salts that are easily soluble in water are not easily soluble in water in alkaline soils, resulting in difficulty in absorbing the kiwifruit tree and causing yellowing.
The amount of fruit-bearing is basically the same under other conditions, the earlier the fruit-hanging, the longer the fruit-bearing time, and the fruit-bearing fruit of the orchard, which has been growing year after year, are heavier, and vice versa.
The use of bulking agents in the production of kiwifruit as an expanding agent will seriously affect the quality of kiwifruit, increase the burden on the tree body, shorten the life span of the tree, and directly lead to the recurrence of yellowing disease in successive years.
Fertilizer application of chemical fertilizers for a single year, especially large amounts of ammonium bicarbonate and urea, results in poor orchard soil fertility, soil fertility, soil nutrient imbalance, and easy to cause damage, burning roots, root rot of kiwifruit, resulting in kiwifruit tree yellow Seriously.
The kiwifruit is watery and afraid of water. Long-term flooding affects the permeability of the soil, which can easily cause root rot, affecting root development and absorption of nutrients. Too much irrigation, overwork and easy to increase soil salinization, resulting in some nutrients such as iron leaching or fixation, prone to iron deficiency yellowing.
The root disease has been examined by the planer for a large number of diseased orchards in the orchards. It has been found that the root rot is relatively common and is characterized by undeveloped roots, less root hair, and more roots, resulting in more fertilization and less root absorption. Balance, weakened tree vigor, poor resistance, easily lead to yellowing disease. (Agriculture)
Experts on prevention of kiwifruit yellowing
In recent years, kiwifruit yellowing has become a common and important disease in production, and it occurs to varying degrees in most regions. Due to the chlorosis of leaves, the ability of photosynthesis is greatly reduced. Finally, the low yield and poor quality have become a major obstacle to the production of fruit trees.
Experts interpreted the cause of the disease, said Liu Zhande, chief expert of the kiwifruit industry system in Shaanxi Province. The reason for the etiology of kiwifruit yellowing is: First, due to high soil pH (alkaline) or high bicarbonate content in the soil, iron elements are fixed. Roots can't be absorbed and used, or there is a lack of iron in the soil, and roots cannot absorb iron. Secondly, the available water in the soil decreases during drought, and the kiwifruit lacks water absorption, which affects the absorption of mineral elements existing in the ionic state around the plant roots, especially the absorption of iron and magnesium related to the synthesis of chlorophyll. In addition, the roots of kiwifruit are fleshy roots, and the distribution layer is relatively shallow. When the orchard is operated, it is easy to injure the roots, thereby affecting the absorption and transport of nutrients such as water and iron, and it is also prone to iron deficiency yellowing.
How should farmers respond? 1 When kiwifruit is planted, it should try to select sandy loam fields with deep soil, fertile soil, and good permeability. Avoid gardens that have been planted with apples, pears, peaches and other perennial trees and soils; 2 promote balanced fertilization techniques to increase the application of iron fertilizers; 3 control yield, increase vitality, fruit period, kiwifruit trees The yield per mu is 2000-2,500 kg, and the overload is strictly prevented to maintain the robust tree vigor; 4 The irrigation is conducted in a proper period, and the flood irrigation is changed to sub-irrigation of small loquats or irrigation of furrows to avoid excessive irrigation, and in particular to prevent water accumulation, Conditional drip irrigation technology can be adopted; 5 adjust the pH value of the soil. In alkaline soils with a pH above 7.5, it is recommended that sulfur per plant or 1 kg of 8% acetic acid be used to properly reduce the rhizosphere pH; 6 Appropriate top-dressing, the application of annual chemical fertilizers in the early growth stage should be mainly ammonium-based nitrogen fertilizers such as ammonium sulfate or urea, and the use of nitrate nitrogen fertilizers and bicarbonate ammonia should be reduced. The topdressing of iron fertilizers in the soil should be mixed with the decomposed organic humic fertilizers; 7 Chemical control, due to the pathological factors induced by the physiological deficiency syndrome Huanghuashu, root diseases should be radically cured as soon as possible. After removing the diseased roots and scraping the diseased skin, the roots were alternately applied with equal amount of Bordeaux mixture for 2 to 3 times.
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