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.
SCLB – Southern Corn Leaf Blight
Scientific Name: Bipolaris maydis (Cochliobolus heterostrophus)
Type: Fungus
Southern Corn Leaf Blight is a fungal disease that affects the growth of corn and is considered the most devastating disease of corn crop. Southern corn leaf blight occurs commonly in the Southeastern regions of the United States. Symptoms are tan colored lesions on the leaves measuring 1/8 to 1/4 inch wide by 1/8 to 1 inch long. The diamond-shaped elongated shaped lesions begin on the lower leaves and then spread to upper leaves. The disease can cause significant loss of leaves. 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 68-89 F and usually occur when moisture and humidity are very high. 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.
SW - Stewart's Wilt
Scientific Name: Erwinia stewartii
Type: Bacterium
Stewart's Wilt is a disease that affects the growth of corn. Stewart's wilt is common throughout the eastern regions of the United States. The disease is transmitted to corn plants during feeding by adult corn flea beetles. These beetles overwinter in the soil and upon emergence in the spring, commence feeding on the plants, and contaminates corn seedlings. An entire field of corn may become infected in a relatively short period of time. Some or all of the plants may die, and severe yield reductions result. The bacteria is carried in the digestive tract of the corn flea beetle. Beetles feeding on infected corn tissue acquire the bacteria and spread it further. Wilting of foliage is often associated with the infection, plants may be stunted, and in severe cases, death may result. When seedlings and young plants are infected, they will wilt and the main stalks may die. Symptoms include lesions on the leaves. The lesions appear as long wavy streaks that turn yellow and eventually brown. Entire leaves may die if the disease is severe and the stalks may develop fungal rot and become weaken. The disease can cause substantial yield loss due to leaf damage and weakened plants resulting from stalk rot. The infestation year to year depends largely on winter temperatures, and how many beetles carrying the disease survive the winter. Mild winter temperatures favor survival of the beetle, thus the disease can be greater the following spring. When winter temperatures are greater than 24°F during a two month period, a moderate to high risk of Stewart’s wilt is possible. Beetles carrying the bacteria that survive the winter could infect corn plants next spring. Insecticide treatments helps reduce flea beetle populations. The best option is to use hybrid disease resistant varieties.