Harmful symptoms, incidence regularity and control techniques of tea cake disease in tea tree in spring

Tea cake disease is an important disease of tea buds in spring, which occurs in tea gardens all over the country and causes serious harm. The harmful symptoms and prevention techniques of tea cake disease are introduced as follows:

1. Harmful symptoms of tea cake disease

The young leaves are light yellow or reddish brown translucent spots at first, and then gradually expand and sink into a yellowish brown or purplish red round spot with a diameter of 2 to 10 mm. The disease spot on the back of the leaf shows a cake-like process, with gray-white powder, and finally the spot becomes dark brown ulcerative, occasionally with a cake-like process on the front of the leaf, and the back of the leaf is sunken. After the petiole and tender shoots were infected, they swelled and twisted, and in severe cases, the new shoots above the diseased part withered and died. Flower buds and young fruits occasionally get sick.

2. The incidence of tea cake disease.

The pathogen overwintered or oversummer with mycelium in diseased leaves. It is a low temperature and high humidity disease. When the temperature is 18: 20 ℃ and the relative humidity is more than 85%, the overcast, rainy and humid condition is beneficial to the disease. Generally, the disease occurs seriously during the spring tea period from March to May and the autumn tea period from September to October. The disease was serious in hilly and flat tea gardens under rainy conditions, extensive management, weeds, improper fertilization, shaded tea gardens, foggy alpine and high wet concave tea gardens.

3. Prevention and treatment of tea cake disease.

a. Strengthen seedling quarantine to prevent the spread of tea cake pathogen through tea seedling transportation.

b. Removing weeds and withered branches, pruning properly and promoting ventilation and light penetration can reduce the incidence of the disease.

c. Increase the application of phosphorus and potassium fertilizer to improve the disease resistance of tea trees.

d. At the initial stage of the disease, 70% methyl thiophanate wettable powder 1000 / 1500 times or 75% chlorothalonil wettable powder 800 / 1000 times were sprayed 2 times 3 times at intervals of 7 to 10 days.

e. Spray 25% triadimefon (triadimefon) 3500 times liquid at the initial stage of the disease, the residual period is long, spray once during the onset period.

f. Non-picking tea gardens can also be sprayed with 0.6-0.7% lime half-volume Bordeaux solution, 0.2-0.5% copper sulfate solution or 600 times 12% oleic acid copper EC to protect tea trees.

g. If Bordeaux liquid is sprayed in the tea garden, it can be sprayed once before spring tea or after picking tea every season, and can not be picked until 20 days after spraying. Bordeaux liquid is an inorganic copper fungicide. The chemical composition of its active component is CuSO4 ·xCu (OH) 2 ·yCa (OH) 2 ·zH2O. In 1882, the Frenchman A. Migar found its bactericidal effect in Bordeaux, so it is called Bordeaux liquid. It is a sky blue colloidal suspension made of about 500 grams of copper sulfate, 500 grams of hydrated lime and 50 kilograms of water. The ingredient ratio can be increased or decreased according to the need. It is generally alkaline and has good adhesion properties, but the physical properties of long-term exposure are destroyed, so it is suitable to be used or made of dehydrated Bordeaux powder. Mix it with water when in use.)