Viral diseases in plants typically affect the young parts, causing symptoms such as smaller and deformed leaves, brown discoloration, stunted growth, and even leaf, flower, or fruit drop in severe cases. In the early stages of infection, the leaf veins lose their green color and begin to shrink. As the disease progresses, the leaves become thickened, with curled edges that form a cup-like shape. Yellow tea leaf disease causes overall chlorosis (yellowing) of the leaves, with the edges curling backward. When the virus affects the fruit, dark green and light green spots appear, along with warty ridges. If the tea root is affected, the pedicel and stalk turn grayish-brown, lose their shine, and become corky and hardened. The virus also damages the main leaf veins, causing brown or black necrosis that spreads to lateral branches, main stems, and growing points. Ocheriferous leaf disease can cause grayish-brown or brown patches on the underside of leaves, often with an oily sheen.
Prevention and control of viral diseases involve several key strategies. First, selecting resistant varieties such as Zhongjiao No. 2, Jinjiao No. 3, Shenjiao No. 1 and No. 2, and sweet pepper No. 1 can significantly reduce the risk of infection. Second, seed disinfection is essential—soaking seeds in a 10% sodium phosphate solution for 20 minutes, followed by thorough washing and germination. Third, proper cultivation techniques, like using plastic mulch to promote early growth and yield, help minimize damage. Fourth, chemical control measures include spraying solutions such as 20% virus A wettable powder diluted 500 times, 50% bacterial clear at 200 times, and 200 grams of poison per liter of water. These should be applied once every 10 days during the seedling stage or after planting, with 3–4 applications in total.
For yellow tea leaf disease, it’s important to remove weeds around fields and clear debris to eliminate overwintering sites for pests. Immediate chemical control is necessary when the disease is detected. Effective options include 15% fluorenone EC diluted 300 times, 34% locust ricin EC at 2000–2500 times, 48% LST at 1000 times, 1.8% Ji Insect moth, 1.8% avermectin (such as Zizao or Xinke) at 3000 times, 15% Qiaoling EC at 1500 times, 73% Ketel EC at 2000 times, 15% broom NET at 2000 times, and 35% special insecticide emulsion oil at 1000 times. When applying these, focus on the upper, tender parts of the plant. For organic or pollution-free vegetable production, dicofol should not be used to control aphids due to its environmental impact.
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