What are the methods for controlling azalea diseases?

The main diseases of azaleas include root rot, brown spot, black spot, leaf blight, and iron-deficiency chlorosis.
  
After an azalea contracts root rot, its growth weakens, the leaves wilt and dry up, water-soaked brown patches appear on the root surface, and in severe cases soft rot develops, gradually decaying and peeling away, with the xylem turning black. This disease is most likely to occur in environments with high temperature and high humidity.
  
The control method is to strictly disinfect the potting soil before repotting, and to keep the soil loose, moist, and well aerated, avoiding waterlogging. If an affected plant is found, promptly deal with the diseased plant and the potting soil. For treatment, the diseased plant can be washed with a 0.1% potassium permanganate aqueous solution or 2% ferrous sulfate, then rinsed with clean water and repotted. A solution made from 70% thiophanate-methyl wettable powder plus 1000 times water sprayed on the potting soil can cure it.
  
Brown spot is one of the main diseases of azaleas. When the disease first appears, small brown spots appear on the leaf surface and gradually develop into irregular large spots; many small black or grayish-brown dots form on the lesions, causing the affected leaves to turn yellow and drop off, affecting flowering that year and the development of flower buds the following year. This disease often occurs during the plum rain season when humidity is high.
  
The treatment method is to routinely ensure the plant has good ventilation and light, prevent excessive humidity, and apply more organic fertilizer and a mixed fertilizer of nitrogen, phosphorus, and potassium to enhance the plant's resistance to infection and its growth capacity. If diseased leaves are found, promptly remove them and burn them in a centralized manner. In the early stage of the disease, spray 0.5% Bordeaux mixture or 0.4 degrees Baume lime sulfur mixture, and add 4% flour to increase adhesion. Leaf spot and black spot can also be treated by the same method.
  
Iron-deficiency chlorosis often occurs in areas where the soil is alkaline. In mild cases, only delayed greening of the plant appears; in severe cases, the leaf tissue can all turn yellow and the leaf margins become scorched and withered. When the disease occurs, it is most obvious on the leaves at the top shoots of the plant, and is generally caused by internal iron deficiency.
  
The control method is to change the iron-deficient nature of the soil and reduce soil alkalinity. Apply more organic fertilizer to improve clayey soil. For iron-deficient plants, 0.2%-0.3% ferrous sulfate solution can be sprayed directly. Alternatively, use chopsticks to poke several holes about 15 cm deep in the soil around the plant, then slowly pour in a 1:30 ferrous sulfate aqueous solution to fill the holes, thereby increasing soil acidity and reducing alkalinity.
  
The occurrence situation and environmental conditions of azalea black spot are similar to those of brown spot, and similar methods can also be used for its control.