Control Methods for Sweet Potato Wrinkle Mosaic Disease

Sweet potato wrinkle mosaic disease, also known as sweet potato latent virus disease. 

[Virus English name] Sweet potato latent virus, abbreviated SPLV. 

[Host crops] Sweet potato, Convolvulaceae, Chenopodiaceae, and some Solanaceae crops. 

[Disease diagnosis] During the seedling-raising period, diseased seed potatoes sprout in greater numbers than healthy potatoes; the leaves of diseased seedlings are initially wrinkled and small, with pale yellow, transparent veins, and later the leaves often form a mosaic of light green and dark green. After diseased seedlings are transplanted into the field, the leaf margins of diseased plants are mostly notched or irregular in shape, and the leaves are markedly wrinkled and small. Severely diseased plants have shortened vines, wrinkled mosaic leaves, and wilt and die. Mildly diseased plants can still continue to grow; at high temperatures above 30°C the symptoms recede, and newly grown leaves are difficult to distinguish from those of healthy plants. When the temperature drops, the lateral branches and side shoots growing from the vine tips and axillary buds again show mosaic and wrinkle symptoms. Diseased plants can still form tubers, but the tubers are small and deformed. The causal pathogen is sweet potato latent virus, and the virus particles are curved, long, rod-shaped, about 700-750 nanometers long. 

[Disease occurrence pattern] Virus-carrying tubers are the main source of the disease. All seedlings raised from diseased potatoes are diseased seedlings, and diseased seedlings planted in the field in turn produce virus-carrying tubers; virus-carrying seed potatoes and potato seedlings can spread over long distances. During seedling collection, the disease can also spread through contact with the sap of cut seedlings; aphids, whiteflies, and other field insects do not transmit the virus. The symptom expression of diseased plants is closely related to temperature; symptoms are especially obvious at about 20-25°C, and become latent above 30°C. In addition, symptoms are also related to soil, cropping system, planting time, and so on. 

[Control measures] (1) Select disease-resistant varieties, such as Xushu 18, Lushu No. 7, and Beijing 553. (2) It is best to use virus-free-treated potato seedlings. (3) Strengthen seedbed inspection, and when diseased seedlings are found, dig them out together with the tubers. When diseased plants are found in the field, pull them out promptly and replant healthy seedlings. (4) Strengthen fertilizer and water management to improve plant disease resistance. (5) At the early stage of disease onset, promptly spray 15% Bingdubike wettable powder at 600 times dilution, or 20% Bingduning water-soluble powder at 500 times dilution, or 10% Bingduwang wettable powder at 500 times dilution, or 83 Zengkangji at 100 times dilution.