NCLB – Northern Corn Leaf Blight
Scientific Name: Exserohilum turcicum
Type: Fungus
Northern Corn Leaf Blight is a fungal disease that affects the growth of corn. Northern corn leaf blight occurs commonly in the Midwestern regions of the United States. Symptoms are cigar-shaped or elliptical shaped gray-green lesions on the leaves that range from 1 to 7 inches long. Lesions begin on the lower leaves and then spread to upper leaves. Severe symptoms can progress rapidly, resulting in blighted leaves. Lesions can also be found on the husk of ears or the leaf sheaths. It can cause significant yield loss in corn. Losses are greater and more severe when plants are infected at the early stage of growth. The disease will spread by rain or wind. The disease is favorable when temperatures are 64-81 F and usually occur when moisture and humidity are very high. Plants usually become infected when water is present on the leaf surface for 6 to 18 hours. Plan on using a 3 year crop rotation and avoid planting in the same location, year after year, as the disease can survive in over winter on corn leaf debris. Proper tillage practices may be helpful in managing the disease. Fungicides can help manage the disease. The best option is to use hybrid disease resistant varieties.
R - Rust
Scientific Name: Puccinia asparagi, Puccinia sorghi
Type: Fungus
Rust, also known as Common Rust, is a world-wide soil borne disease that affects the growth of asparagus, cantaloupes & melons, corn, and lettuce. It is one of the most destructive disease in growing asparagus in the United States. The disease affects the ferns on asparagus. Lesions develop and turn cream-orange color, then turn a reddish-brown color, then eventually turn a brick red or rust color. During the winter the lesions will turn a black color. Severe infestation stunts or kills young asparagus shoots. The infected plants should be removed to avoid further infestation. When corn is infected the disease affects the upper and lower leaf surfaces, where small specks appear on the leaves, then develops into small tan spots, and distinguished by cinnamon-brown pustules. These pustules blister and turn dark brown to black late in the season. Corn stalks are weakened and stalk rot potential increases. Significant damage to upper leaves results in significant yield losses. Common rust spreads by windblown spores. The disease is also favorable cool and moist conditions when temperatures are 68-72 F, and usually occurs when there is nine hours of wet weather. The best option is to maximize air movement between the plants and to use disease resistant varieties.
S - Smut
Scientific Name: Urocystis cepulae or Urocystis colhici
Type: Fungus
Smut is a world-wide 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 disease in growing onions in 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 acceptable 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 weaken 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 occur in the spring. If the soil temperature is above 84%, 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.