This disease is common in southern China, which can cause the leaves of oleander to wither and fall early. The pathogen of this disease mostly invades from the tip and edge of oleander leaves. There will be purplish red spots on the leaves with brown spot disease, and then gradually expand into round, semi-circular or irregular shaped patches, with raised rings on them. The lesions were brown and wide.
In the area with serious disease, spray 600 times of 40% polysulfide suspension, 500-800 times of 30% cupric oxychloride, 800-1000 times of 50% carbendazim wettable powder, 1000 times of 70% methyltobuzin wettable powder, 800-1000 times of carbendazim every 10 days, 2-3 times in total.
The main diseases of oleander. When axillary buds and adventitious buds germinate in large numbers, many delicate twigs will cluster, resulting in shortened internodes and smaller leaves. The diseased twigs will sprout again, and the base of the new twigs will be swollen, showing reddish color, often clustering. Twigs die in winter, and more twigs will be produced next year, which will happen again and again, finally causing the whole plant to die.
When individual branches start to show symptoms, they should be cut off and destroyed in time; when aphids and leafhoppers are found to be harmful, they should be killed in time; after the disease, tetracycline and other antibiotics can be used for prevention and control -- two holes can be drilled in the upper and lower sides of the diseased branches at the base of the trunk to the xylem, and 1000-2000 units of tetracycline or terramycin solution can be slowly injected into the xylem with syringes, and the injection amount depends on the plant size and disease. Depending on the situation, the dosage per plant is generally 30-50ML.
The spot is located at the edge or middle of the leaf blade, semicircle or circle. When several disease spots are connected, they are wavy, both positive and negative, the color of the front is darker than the back, and the disease spots are gray white or gray brown; in the later stage, the disease spots produce black powdery mildew layer, which generally occurs on the overwintering leaves.
High temperature and high humidity are easy to cause the disease and damage the leaves. After the onset of the disease, 50% carbendazim 500 times or tolbutine 600 times can be used for spraying. Other control methods can refer to Camellia pest control.
