First, the symptoms
Mainly in the newly extracted shoots. The tips of the new shoots are bright yellow with green veins on both sides of the veins. In severe cases, the leaves become light yellow or yellow-white, and irregular necrotic spots occur at the margins and tips of the later leaves.
Damaged shoots have a small amount of growth and their spikes turn yellow. The fruit set-up rate is low, the fruit size is small, and sometimes all buds fall.
Second, the pathogen
Physiological diseases caused by iron deficiency. The function of iron in plants is to promote the activity of many kinds of enzymes. When the iron content in the soil is insufficient, the growth and development of the trees and the production of chlorophyll are hindered, thus forming iron deficiency yellow leaf disease.
Third, the incidence conditions
1, the lack of iron in the soil, there are many reasons, the most important of which is the soil pH and redox process. In the high pH soil, oxidation is the main process, so that iron precipitation and fixation are the main causes of iron deficiency yellow leaf disease. If the soil contains lime, calcium, and too much iron, iron can be converted into insoluble compounds and the plants cannot absorb iron for normal metabolism.
2. Poor soil conditions limit root absorption of iron, not necessarily the lack of iron in the soil. Such as soil viscosity, poor drainage, long periods of low temperature in spring, slow temperature rise, etc. all affect the root absorption of iron.
3. The age of trees and the amount of results have a certain impact on the incidence, generally with the increase of the age of the trees and the increase of the amount of results, the severity of the disease is significantly increased.
Because iron cannot move from one tissue to another in plants, iron deficiency first manifests on the young leaves at the tip of the shoot. This is also one of the main differences between the disease and other yellow leaf diseases.
Fourth, prevention and control measures
1. Spray the foliage, when the leaves appear yellow leaves, spray EDTA iron + 0.15% citric acid, and then spray once every 10-15 days.
2. Spread the buds. After pruning in winter, spread the shoots with EDTA iron + 25% citric acid mixture.
3. Ferrous sulphate is applied to the soil. Before the budding of the grapes, the sulphate is applied on both sides of the rack. The sulphate is applied to the sulphate. 0.2-0.3 kilograms per plant is applied. If the sulphate is mixed with the organic fertilizer, the application effect will be better.
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