Northern Corn Leaf Blight
Northern Corn Leaf Blight (NCLB)
Symptoms
Symptoms of NCLB can often be confused with symptoms of bacterial wilt, especially late in the season. Lesions are long (1" to 6") elliptical in shape with pointed ends, grayish-green or tan in color and develop first on lower leaves.
Northern Corn Leaf Blight
Paul Vincelli, University of KY
NCLB lesions differ from bacterial wilt lesions in that they are generally definite in shape, have greater width and do not follow leaf veins for extended lengths. The disease progresses upward.
During damp weather, greenish black fungal sporulation is produced in NCLB lesions. On hybrids carrying an Ht2 resistance gene, long yellow to tan lesions with wavy margins and no sporulation have been observed on infected leaves. These resistance-reaction lesions can be easily confused with Stewart's Wilt (bacterial wilt).
Cause
Symptoms of NCLB are caused by the fungus Setosphaeria turcica (Exserohilum turcicum, Helminthosporium turcicum). Look for this disease developing first on lower leaves when corn plants are from waist to shoulder high. Development of the disease is favored during periods of wet weather with moderate temperatures during the growing season.
The fungal mycelia and conidia can overwinter in plant debris, and the disease is later tranferred by wind to new plants. Severe yield loss can occur when leaves become blighted during early grain fill. NCLB will be more severe in fields with corn following corn under reduced tillage. Other hosts include sorghum, johnsongrass, and some other grass species.
IPM Techniques
- Examine plants every four weeks from whorl through dent stage. Observe two rows of plants 10 feet in length at several representative locations. The number of random sites you should observe when scouting a field is based on the size of the field. To determine the number of scouting sites see Scouting Corn .
- Report the severity of the disease according to the following rating scale:
0 = no symptoms
1 = a few lesions on lower leaves of some plants
2 = nearly all plants have some lesions and lesions are not confined to only lower leaves
3 = all plants have lesions on nearly all leaves, some or all leaves dried up and killed
- Plant resistant hybrids, especially when grown without rotation under reduced tillage.
- Rotate away from corn and sorghum for 1 - 2 years.
References and Additional Information
- IPM-2 Kentucky IPM Manual for Corn
- PPA-10a Kentucky Plant Disease Management Guide for Corn and Sorghum by P. Vincelli and D.E. Hershman, Extension Plant Pathologists
Compendium of Corn Diseases. M.C. Shurtleff. The Amer. Phytopathol. Soc. 1980
