The past several weeks have been rough on the green tissue of corn leaves.

Corn blotch leaf miners have removed much lower green leaf tissue on some of the continuous cornfields, particularly where there was heavy corn residue from the previous year. This is one of the most discussed insect issues this summer. Several promising insecticide treatments may be used more in the future. This insect is increasing in severity and not being controlled adequately by predators prior to significant foliar damage.

Spider mites built up rapidly with hot conditions, but have now larger died back. However, foliar damage is done and plant health may be compromised later into September.

Southern leaf rust increased rapidly 7-14 days ago during a very humid and hot 95-degree-plus temperature period. Susceptible hybrids have dense areas of rust pustules up to the ear leaf and beyond in some cases.

Gray leaf spot disease continues to build on many corn hybrids. Even with the low rainfall conditions throughout much of the summer, it built up surprisingly well on the upper leaves. Those lesions are now elongating. It will be a race to physiological maturity for the plants before significant green tissue is covered by this disease.

More late second generation corn borer are present in the untreated non-Bt corn fields than most realize. Tops are beginning to go out and stalk rot and premature death will begin occurring in those fields.

Fields need to be closed monitored yet to prioritize them for early harvest if needed.

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