Why do all the lotus leaves turn gray? What kind of disease is this? What medicine should I take?

First, lotus root brown spot disease. A common disease of lotus leaves, which produces light brown spots on the leaves and makes the diseased leaves dry locally. Prevention and control: reasonable close planting to ensure ventilation and light transmission of lotus field; Appropriately increase the application amount of phosphorus and potassium fertilizer, improve the stress resistance of plants, and remove the diseased plant residues in time. Spraying 600 times of 25% carbendazim or 1000 times of 75% chlorothalonil at the initial stage of the disease.

Second, lotus root black spot disease. Also known as brown streak, it only occurs on leaves. In severe cases, the lesions converge and the leaves turn yellow. Prevention and control: thoroughly remove diseased leaves in the field in winter and burn them centrally. At the early stage of the disease, the diseased leaves were removed and sprayed with drugs for prevention and treatment. Commonly used 70% thiophanate methyl 1000 times solution, or 65% zineb 600 times solution, or 1: 160-200 times bordeaux solution, once every 10- 15 days.

Third, lotus root rot. Also known as Fusarium wilt, it infects underground stems and causes rot. In severe cases, the whole field is yellow and still burning. Prevention and control: 2-3 years rotation in seriously ill fields. 70% thiophanate-methyl 1000 times solution or 75% chlorothalonil 800 times solution is commonly used to spray the seeds, cover them with plastic film for 24 hours, and then plant them after drying. The lotus field is deeply ploughed, and lime 150kg is applied per mu. At the beginning, 0.5 kg of 75% chlorothalonil and 30 kg of dry soil can be mixed and scattered in shallow water fields.

Four, lotus leaf stripe virus disease. Symptoms can be seen on damaged lotus leaves and underground rhizomes, with large polygonal to irregular light brown spots on the leaves and dark brown anthrax stripes on the epidermis of rhizomes. Control: Select disease-resistant varieties, control aphids (virus vectors) in time, and spray 1.5% plant protection emulsion 1000 times at the initial stage of the disease.

Five, lotus leaf blight. The damaged lotus leaves are brown and withered, which affects the growth of lotus roots and reduces production. Prevention and control: keep the lotus field clean and prevent it from being polluted by oil pollution. Sewage and soapy water can also cause lotus leaves to wither and die. Lotus root is very sensitive to herbicides, so don't use herbicides in lotus root fields.

The common diseases of lotus root are mainly lotus leaf erosion and loss of photosynthesis. Even if the lotus root does not die, it will not grow up, so there will be no yield. Therefore, it is necessary to pay attention to the abnormality of lotus leaf and treat it in time.