With late plantings and a wet spring, this year has created disease conditions in areas with:
- Wet, humid soils combined with recent high temperatures
- Fields with high residue
- Reduced or no-till ground
Anthracnose is among the diseases that thrive in these conditions. It’s caused by a fungus and can affect the plant at any stage of growth. Look for these symptoms: leaf blight, stalk rot, top-kill of the stalk, and kernel rot. The disease causes the most problems at the leaf blight and stalk rot stages.
ABOVE: Anthracnose leaf blight (Ohio State University)
ABOVE: Anthracnose stalk rot (Ohio State University)
Grey Leaf Spot can be easily confused with other types of disease in its first stages of development. The tell-tale sign for this disease is small lesions surrounded by yellow rings or halos. The fungus will begin in the lower leaves and move to the top of the plant. Lesions travel through the tissues in the leaf, elongating and eventually merging together. The plants then become much more susceptible to other disease such as stalk rot.
ABOVE: Gray Leaf Spot
Northern Leaf Spot is a fungal disease that, like Grey Leaf Spot (GLS), is identifiable by its narrow elongated shaped lesions surrounded by a pigmented border. The disease will spread to all parts of the plant including leaves, sheaths, husks, and ears. Spores are released and are capable of traveling and infecting neighboring fields.
ABOVE: Northern leaf spot (Ohio State University)
For each of these specific diseases, I recommend control methods of fungicides or resistant/tolerant hybrids. For more information on these and other mid-season corn diseases, Purdue University’s Desktop Reference link is a great resource.