It mainly damages leaves and also infects petioles and stems. At the initial stage, the leaf surface produces nearly round white spots, which are rapidly expanded and connected into pieces. It is a large white powder area with no obvious edge, which is covered with white powdery mildew. In severe cases, the leaves are yellow and withered. Law of onset: high air humidity. When the temperature is high, it is beneficial to the occurrence of disease.
Pay attention to ventilation and light transmission, avoid planting too dense, remove and burn the early diseased leaves. In the early stage of the disease, spray 800-1000 times of 50% of the bacteriophage, or 0.1-0.3 of Baume's stone sulfur mixture, or 600-800 times of chlorothalonil, once a week, 2-3 times in a row.
When the petals are damaged, they will produce water stained spots, which will soon expand and turn brown and rotten. When the leaf is damaged, brown and soft spots appear at the edge, and then extend to the whole leaf. When the weather is wet, it is covered with grey mould layer and then becomes brown and dry. The law of disease: the pathogen overwinters with sclerotia, the temperature is 20 ℃, the humidity is high, easy to get disease.
Improve the temperature and humidity of the environment, and pay attention to ventilation and light transmission. At the early stage of the disease, spray 600-800 times of Shengling or 800 times of methyltobujin wettable powder. Once a week, three to four times in a row.
The damaged plants grew dark green at the base of the stem near the soil surface, and they were brown and rotten after expanding. In the morning, white filaments can be seen in the disease spot when it is wet, and the seriously injured plant is lodging. Most of the diseases occur in rainy weather, too much water and soil water.
Strengthen the management during the onset of the disease. When the air humidity is high, less or no water should be poured in order to keep the soil in the basin moist. Less nitrogen, more phosphorus and potassium. Remove the diseased leaves and old leaves in contact with the soil in time. After the onset of the disease, spray 65% diclosone 500-700 times solution, or use chlorothalonil 600-800 times solution.
