Responsible for over 64 million bushels of yield loss annually, northern corn leaf blight (NCLB) is the third most destructive disease in corn behind tar spot and southern rust, according to Crop Protection Network’s 2024 yield loss report.¹
Northern corn leaf blight infections harm yield by reducing green leaf area and photosynthesis, impairing grain fill. The damage can also extend to standability problems as plants compensate for energy lost through leaf damage by drawing energy from the stalk. If infection occurs before tasseling, yield losses can reach 50%.² With later infections, losses are typically lower.
What are the symptoms of northern corn leaf blight?
Early northern corn leaf blight symptoms appear on a plant’s lowest leaves in the form of elliptical green-gray, cigar-shaped lesions up to six inches long. Lesions run parallel to leaf margins and often turn tan or gray. When humidity is high, black or green fungal spores can appear, darkening the lesions.
The lesions can eventually grow, which can cause leaves to die. The infection will usually work its way upward in the plant, and leaf lesions can lead to stalk rot and, eventually, plant lodging.
The cigar-shaped lesions of NCLB distinguish it from another common corn leaf disease, gray leaf spot, whose lesions are more rectangular.
How does northern corn leaf blight spread?
The fungus that causes northern corn leaf blight overwinters in corn residue, and spores are dispersed by wind and splashing water, meaning that weather, humidity and rain are big factors in how much NCLB spreads in any given year. NCLB prefers long periods of dampness, including high humidity and extended dews, and mild temperatures from the mid-60s to low 80s. Since northern corn leaf blight spores overwinter in corn residue and surface soil, the disease thrives in continuous-corn and low- to no-tillage operations.
Northern corn leaf blight scouting and treatment
Managing northern corn leaf blight requires vigilance on a number of fronts, from seed hybrid choices to careful scouting, fungicide application, cultural practices and more.
Scouting for NCLB
NCLB infections can occur a week or two before the tell-tale cigar-shaped lesions become noticeable, and it’s recommended to scout for symptoms regularly beginning around V14, just before tasseling.
Staying in front of NCLB with preventive fungicide application
Fungicides can help control northern corn leaf blight in both low- and high-pressure environments and limit negative yield impacts. When scouting and weather conditions show a high potential for the development of NCLB, a fungicide application for leaf blight is typically most effective if applied during tasseling to early silking stages (VT-R1).³
BASF’s Headline AMP® Fungicide, Priaxor® Fungicide, Veltyma® Fungicide and Revytek® Fungicide are all labeled for use to combat northern corn leaf blight.
Cultural practices
Using tillage to bury crop residue that is harboring northern corn leaf blight spores can be useful to reduce disease pressure in the following crop. Rotating from corn for a season — to soybeans, for instance — and tilling before planting corn again can help keep down disease levels in that new corn crop as well.
Choosing seed hybrids
Choosing hybrids with varying levels of resistance to NCLB, including resistance to specific genetic types of the northern corn leaf blight fungus (HT genes), can be effective in keeping impact of NCLB to a minimum.
Northern corn leaf blight is just one of the many corn diseases to keep in mind, scout for, and take steps to manage — or run the risk of incurring substantial yield losses.
To learn more specifics regarding hybrid selection, fungicide treatments and timing to protect against northern corn leaf blight and more, consult with your local retailer or your regional BASF representative.
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Endnotes
- “Corn Disease Loss Estimates from the United States and Ontario, Canada — 2024.” Crop Protection Network, 18 Feb. 2025, cropprotectionnetwork.org/publications/corn-disease-loss-estimates-from-the-united-states-and-ontario-canada-2024. Accessed 25 Feb. 2026.
- Kleczewski, Nathan. “Northern Corn Leaf Blight.” University of Delaware, Oct. 2025, www.udel.edu/academics/colleges/canr/cooperative-extension/fact-sheets/northern-corn-leaf-blight/. Accessed 20 Feb. 2026.
- “Fungicide Efficacy for Control of Corn Foliar Diseases.” Crop Protection Network, 2026, cropprotectionnetwork.s3.amazonaws.com/corn-foliar-efficacy-guide-2026.pdf. Accessed 25 Feb. 2026.
