How to Treat Grape Yellow Spot Disease
Grape yellow spot disease is a common physiological disease that troubles fruit farmers, characterized by chlorosis and yellowing of leaves and reduced photosynthetic efficiency. This article systematically analyzes the scientific response strategies for grape yellow spot disease from the pathogenesis to the comprehensive prevention and treatment plan.
Analysis of the Pathogenic Mechanism of Grape Yellow Spot Disease
Difference in Variety Resistance
Varieties such as巨峰 (Jufeng) and 夏黑 (Xiahei) have weaker resistance to yellow spot disease, with larger intercellular spaces in leaf epidermal cells, making it easier for pathogens to invade. On the other hand, varieties like 赤霞珠 (Chixiazhhu) and 霞多丽 (Xiaduli) show stronger resistance, which is closely related to the thickness of the leaf cuticle layer.
Analysis of Climatic Triggers
Continuous rainfall during the rainy season leads to an increase in soil pH (an average increase of 0.5-1.2), and a reduction in the availability of iron elements by 45%-60%. When the air humidity remains above 80% for 72 consecutive hours, the incidence of secondary diseases such as downy mildew triples, exacerbating the nutritional consumption of the plants.
Soil Environment Imbalance
In the North China and Northwest regions, when the soil pH is greater than 7.5, the available iron content is less than 3mg/kg (normal value is 5-8mg/kg). At this time, for every 1% increase in the content of calcium carbonate in the soil, the availability of iron elements decreases by about 12%.
Comprehensive Prevention and Control System for Grape Yellow Spot Disease
Nutrition Management Plan
Applying decomposed sheep manure (3m³/acre) combined with chelated iron fertilizer (EDDHA-Fe 200g/acre) during the germination period can increase chlorophyll content by 35%. During the color change period, spray 0.2% ferrous sulfate + 0.1% citric acid mixture on the leaves, with a 10-day interval for two consecutive sprays.
Soil Improvement Technology
Applying sulfur powder (15kg/acre) during the autumn deep plowing can reduce the soil pH by 0.8-1.5. Combined with the use of bio-fertilizer (Bacillus subtilis ≥200 million/g), it can increase the availability of iron elements by up to 40%.
Chemical Control Strategy
In the early stage of the disease, use a 27.12% basic copper sulfate SC solution diluted 800 times, focusing on the back of the leaves. In severe cases, alternate the use of a 10% difenoconazole WG solution diluted 1500 times and a 25% azoxystrobin SC solution diluted 2000 times, once every 7 days for three consecutive times.
By adopting a three-in-one prevention and control system that includes variety selection, soil improvement, and precision medication, the incidence of grape yellow spot disease can be effectively controlled. It is recommended to test the soil pH after the leaves fall each year, maintaining it within the appropriate range of 5.8-6.5, to fundamentally prevent the occurrence of physiological yellowing.