Northern Corn Leaf Blight – Be Ready for August

By: Craig Allaman, Agronomist at Cornelius Seed

As we head into August, I’m keeping a close eye on Northern Corn Leaf Blight (NCLB). Right now, I’m seeing minimal NCLB in fields, but don’t let that fool you. Once temperatures moderate next month, this disease will start cycling again, and combined with threats like Southern Rust and Tar Spot, it could spell trouble for your corn yields. As your agronomist, I want to make sure you’re prepared.

Why Northern Corn Leaf Blight Matters

NCLB, caused by Exserohilum turcicum, shows up as long, cigar-shaped lesions on leaves, often with a grayish-white center. It loves cooler, moist conditions, which we’re likely to see in August. This disease reduces photosynthesis, weakens stalks, and can lead to significant yield losses, especially in susceptible hybrids. When paired with Southern Rust (already active) or Tar Spot (coming soon), the impact can be severe.

How to Stay Ahead

• Fungicide Timing: Apply a long-residual fungicide at the R1 stage to control NCLB before it takes hold. These fungicides are effective against multiple diseases, including Southern Rust and GLS, so you’re covering multiple bases. If you’ve already applied one, keep scouting to monitor disease pressure.
• Resistant Hybrids:  Hybrids with strong disease tolerance (e.g., for GLS or Anthracnose Stalk Rot) often perform well against NCLB. Look at C5704, C6007, C6203, C6523, C6713, C7026, C7235, and C7399 (rated Excellent or Very Good for GLS or Anthracnose Stalk Rot). These are solid choices for disease-prone areas. Review our Product Guide to find hybrids with good NCLB ratings.
• Scout and Report: NCLB can sneak up in August, so scout regularly, especially in fields with a history of the disease. If you spot those cigar-shaped lesions, let our team know. We’re working to update hybrid ratings for diseases like NCLB to better guide your decisions.

The Bigger Picture

August is a critical month. Southern Rust is already spreading, GLS is active in central Iowa, and Tar Spot will likely join the mix as temperatures cool. NCLB thrives in these conditions, so proactive management is essential to protect your yields.

Get Prepared

Review our Product Guide to find hybrids with good NCLB ratings for next year. Scout your fields, apply long-residual fungicides at R1, and reach out to us at Cornelius Seed for tailored recommendations. Let’s keep NCLB from derailing your 2025 or 2026 season!