What is the matter with yellow spots on grape leaves?
The appearance of yellow spots on grape leaves is a common problem during planting. It not only affects photosynthesis, but also directly affects fruit quality. As a typical physiological disease, yellow leaf disease is often closely related to cultivation and management. Only by mastering scientific prevention and control methods can grape plants resume healthy growth. The three major causes of grape yellow leaf disease are unbalanced. Soil environment is unbalanced. When the soil pH value is greater than 7.5, too high calcium carbonate content will lead to the solidification of iron. Experimental data show that when the soil available iron content is less than 4.5 mg/kg, new leaves of grapes will show typical network yellowing. It is recommended to use pH paper to test the soil pH value every spring and adjust it with the application of additional sulfur powder. Wrong fertilization method Undecomposed organic fertilizers (such as chicken manure and sheep manure) contain a large number of pathogenic bacteria and ammonia gas. Direct application will burn the roots. A 2018 study by the Hebei Academy of Agricultural Sciences showed that applying cow dung that has been decomposed for more than 3 months can reduce the incidence of yellow leaf disease by 67%. It is recommended to use EM bacterial composting technology to ensure complete decomposition of fertilizers. Improper water management, newly transplanted seedlings have weak root absorption capacity, and soil water content should be maintained at 60-70%. When using a drip irrigation system, it is recommended to irrigate twice a day for 1 hour each time. Adult plants need the greatest water during the swelling period, when lack of water can easily cause yellowing of old leaves. Systematic control plan for grape yellow leaf disease three-step soil improvement, an 80-cm deep trench was opened before planting, and water was poured into salt for three times. Applying 5 tons of decomposed pine needles +20kg of ferrous sulfate to every 667㎡ can significantly improve the activity of iron elements. After applying this method in vineyards in 2019 (X-J), the soil available iron content increased by 3.2 times. Precision fertilization strategy When applying base fertilizer in autumn, decomposed sheep manure is buried and applied according to the standard of 10kg per plant, combined with 2 kg of calcium-magnesium phosphate fertilizer. The "3+2" model is adopted for topdressing during the growth period: 3 times of water-soluble fertilizer (germination, fruit setting, color turning period)+2 times of foliar fertilizer (0.3% ferrous sulfate +0.1% citric acid solution). In the early stage of the disease, 1000 times EDDHA iron chelate solution was used to combine amino acid foliar fertilizer with chemical control and sprayed three times in a row at an interval of 7 days. Focus on spraying the back of leaves and choose to apply the application before 10 a.m. on cloudy days. Severely yellowed plants need to be irrigated with roots, and each plant is irrigated with 50L of liquid medicine.
Through a three-in-one solution of soil improvement, fertilizer and water regulation, and chemical control, grape yellow leaf disease can be effectively controlled. It is recommended to establish a planting log to record each fertilization and medication use, and adjust management measures in a timely manner based on leaf color changes. Regularly detect soil EC values and trace element content to achieve precise management.