S - Smut Resistant Onions

S - Smut Resistant Onions. Scientific Name: Urocystis cepulae or Urocystis colhici. Type: Fungus. Smut is a worldwide soil-borne disease that affects the growth of cantaloupes & melons, leeks, onions, and shallots. Smut has not been found in chives and garlic. It is one of the most destructive diseases of growing onions in the northern parts of the United States. The disease infects plants only when they are seedlings, killing the plants early in the season. Symptoms of smut include black streaks, blisters, or lesions appearing on the young leaves near the bulbs. A black powdery spore mass will be released when the bulbs rupture. Cold, damp weather in the spring can make the seedling susceptible to the disease. Once affected by the disease, most of the seedlings will die in 3 to 5 weeks after germination. Infected plants may survive in a weakened condition, but the plant growth will be stunted, and the plant will die slowly. The infected plants should be removed and burned on the spot to avoid further infestation. The disease is also favorable when temperatures are 61-72°F, and usually occurs in the spring. If the soil temperature is above 84°F %, when the seedlings are susceptible to the disease, there is usually no infection. Plan on using a 3-year crop rotation and avoid planting onions in the same location, year after year, as the disease can survive in the soil for a long time, up to 15 years. The smut disease can be transmitted from one field to another by water, by wind, and by farm equipment. Once the soil is infected, only seeds treated with fungicide should be planted. The best option is to use disease-resistant varieties.