What disease is a person named Qiuhua whose leaves turn black?

Black spot of chrysanthemum is caused by Fusarium oxysporum infection. It mainly harms chrysanthemum leaves. At the initial stage of leaf injury, there are chlorosis or purple-brown spots, which gradually expand into round, oval or irregular lesions, brown or dark brown, with a diameter of 5-10 mm. The size and color of the lesions are related to chrysanthemum varieties. Multiple lesions can be interconnected to form large plaques. In the later stage, the center of the lesion turned light gray and scattered in small black spots. The diseased plants died in turn from the lower leaves, but they did not fall off. In severe cases, only 2-3 green leaves are left on the upper leaves. The prevention and control methods include pulling out diseased leaves immediately when they are found, watering less or not in rainy days, strengthening water and fertilizer management, paying attention to the proper cooperation of nitrogen, phosphorus and potassium fertilizer, preventing plants from growing white, spraying fungicides when they are ill, selecting varieties with strong resistance, deepening crop rotation, changing soil in pots, and infiltrating sand and nutrient soil for planting.

Preventive and control measures

1, remove the diseased leaves immediately if found. Deep ploughing in winter, burying diseased leaves, or rotating crops. Water less or no water in rainy days, avoid watering your head, and don't get the soil and fields too wet. Potted soil needs new soil every year.

2. Strengthen the management of water and fertilizer, pay attention to the proper cooperation of nitrogen, phosphorus and potassium fertilizer, and prevent plants from growing in vain. Timely irrigation and drainage can promote the robust development of plants and improve their disease resistance.

3. When spraying fungicides in the onset period, 75% chlorothalonil 600-800 times solution, 65% zineb 500-600 times solution and 1% Bordeaux solution can be selected. 1 time for 3-4 times every 7- 10 days, which can reduce the residue of germs.

4. Choose more disease-resistant varieties, implement crop rotation and deep ploughing, change pots and soil, and infiltrate sandy nutrient soil for planting. Potted soil, field soil and garden soil should be disinfected by spraying chemicals, and healthy aseptic seedlings should be used as breeding materials. If the old plant carries bacteria, the foot buds far away from the mother plant should be selected and impregnated with chemical agents for disinfection.