Five signs of foliar disease to look for when harvesting corn

By Andi Anderson

Corn harvest is a time to celebrate the fruits of your labor, but it's also an opportunity to scout for signs of foliar disease. Identifying diseases at harvest can help you predict which diseases your fields may face in the next growing season and adjust your fungicide program accordingly.

Here are five signs of foliar disease to look for when harvesting corn:

1. Stalk lodging: Stalk lodging can be caused by a number of factors, including stalk rot caused by diseases such as anthracnose. If you see stalks lodging during harvest, take note of the severity and location of the problem.

2. Discolored ears: Discolored ears are often a sign of ear rot caused by fungi such as Fusarium or Gibberella. These diseases can continue to grow throughout the fall, causing damage to the ear and increasing the number of mycotoxins present in the grain.

3. Leaf lesions: Leaf lesions can be caused by a number of different diseases, including anthracnose, gray leaf spot, and northern corn leaf blight. Pay attention to the size, shape, and color of the lesions to help you identify the disease.

4. Dead, gray leaves: Dead, gray leaves can be a sign of gray leaf spot, one of the most common corn diseases. Gray leaf spot can reduce yields by up to 40 bushels per acre.

5. Pustules: Pustules, or raised fruiting-bodies, on the surfaces of leaves and husks can be caused by rusts or tar spot. Southern corn rust produces light brown to orange pustules on the top of leaves, while common rust produces dark reddish-brown pustules on both sides of leaves. Tar spot produces firm black dots that cannot be rubbed off.

If you see any of these signs of foliar disease during harvest, be sure to contact your local agronomist or crop advisor for assistance in identifying the disease and developing a management plan for the next growing season.

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