Northern Corn Leaf Blight Identification, Favorable Environment, and Management

Northern Corn Leaf Blight Defined

Northern Corn Leaf Blight (NCLB) is a fungal pathogen that overwinters on infected corn residue. NCLB causes yield loss by reducing the amount of photosynthetic leaf material used to build kernels. Unmanaged or untreated high risk corn acres may see a yield reduction ranging from 15% to 50%. High risk corn acres are defined as continuous corn rotation, minimum tillage, and/or, planted with susceptible corn products.

NCLB Identification

NCLB is identified as tan, cigar shaped lesions near the leaf margins. These cigar shaped lesions can range from 1 to 7 inches long (Figure 1). The centers of the lesion may have black to gray spores, giving the lesion a dirty appearance. Corn plant leaf sheaths and husks can also have lesions. Goss’s bacterial wilt and southern corn leaf blight are common foliar diseases than can be mistaken for NCLB.

NCLB Supporting Environments

When looking at the disease triangle (host, disease, and environment), the environment might be the most important factor for NCLB development. As mentioned, NCLB overwinters on infected corn residue. When spring and summer weather support fungal growth, spores reproduce and splash onto leaves of the current corn crop. Supporting weather conditions include moisture and high humidity with temperatures that range between 64 to 81^o F. Increased plant populations, heavy canopy cover, and low-lying areas of the field are environments that can support continuous moisture and humidity. Therefore, it is important to keep an eye out for NCLB in these types of field areas.

NCLB Management

Cultural management practices are the best control for NCLB. The practice of planting a resistant corn product is one of the best preventative measures. Most corn products used in the northern Midwest have some level of tolerance to help decrease the risk to NCLB infection. Implementing crop rotation helps break the disease cycle. A minimum one-year crop rotation out of corn is recommended for fields that have tillage. In a minimum tillage or no-till cropping system, a two-year crop rotation may be needed. When managing residue, it is best to encourage decomposition of plant material.

Chemical control is also an option for managing NCLB. Currently, an economic damage threshold for NCLB does not exist. Therefore, making an application decision based on field history, product planted and monitoring weather patterns is important. The time to field scout is before or at the VT growth stage. When weather conditions are favorable it is important to continuously scout as lesions may form up to 12 days after infection. Fungicides applied at the VT to R1 growth stages are more likely to have an economic return.

Lindsey Novak
Channel Agronomist

Sources:

De Rossi, R.L., Guerra, F.A., Plazas, M.C., Vuletic, E.E., Brücher, E., Guerra, G.D., and Reis, E.M. 2022. Crop damage, economic losses, and the economic damage threshold for northern corn leaf blight. Crop Protection, Volume 154, April 2022, 105901.

Wise, K. 2011. Northern corn leaf blight. Diseases of Corn. BP-84-W. Purdue University Extension. https://www.extension.purdue.edu/extmedia/BP/BP-84-W.pdf.

Websites verified 1/15/24. 1110_349351