Agronomy Tip: Identify Tar Spot on Corn

Tar spot lesions on corn.

Tar spot disease in corn manifests as small, raised, irregular-shape black lesions scattered across the leaf surface. It spreads from the lowest leaves to the upper leaves, leaf sheaths, and eventually the husks of developing ears.

When you are out in the fields scouting, be aware that these visual symptoms are similar to other pathogens like common and southern rust. An important differentiator is that tar spot lesions may be surrounded by a tan halo and cannot be rubbed off. Should you find tar spot in your fields, contact your seed provider or agronomist to determine next steps.

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