Brian Weller, lead agronomist for Central Farm Service, knows that insects are the concern in a dry year and diseases are your worry in a wet year. Because this spring has been cool and wet, here are some of the diseases that you should be aware of:
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NCLB (Northern Corn Leaf Blight): Long narrow “cigar-shaped” tan or greyish lesions that form parallel to leaf margins; 1 – 7 inches long. In wetter conditions, this pathogen may also create dark spores on the lower leaf surface.
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Eye Spot: small 1/16th inch water soaked circular lesions with a tan center and darker brown margin; the spot is surrounded by a yellow “halo” which looks like an eye when held to the light. Symptoms will usually start to show around 2-3 weeks before tasseling.
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Common and Southern Rust: this spore creates a brown or brownish red sport/pustule that leaves a brown or orange stain when rubbed.
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GLS (Gray Leaf Spot): starts as a small lesion with yellow halos similar to Eye Spot but as the lesions mature they elongate into narrow brown and gray rectangles. These lesions expand out parallel to the vein, are 1.5 – 2 inches long, and will usually start to show around 2-3 weeks before tasseling.
Both NCLB and Gray Leaf Spot can overwinter so if you’ve had either in your field this season, consider the following:
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Rotate to soybeans or another non-host crop the following season.
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Bale leftover corn or plow infected corn into the ground to manage residue and prevent a repeat occurrence.
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Select hybrid seeds that are rated high for these diseases.
As your corn reaches the proverbial “knee high by the fourth of July” stage, take some time to examine it’s condition so that your crop provides the best yield possible.
-Terry Olson, Titan Machinery
References:
https://www.cfscoop.com/News/Agronomy-Update–Corn-Diseases-2018-06-29/1474
www.goldenharvestseeds.com/agronomy/articles/managing-corn-leaf-diseases-for-2018