Weekly Scouting Report - September, 16, 2014
Hello everyone. I hope everyone survived the wet season we witnessed last week. With that said there was not much scouting that went on, but there was a lot of discussion throughout my network about the amount of Anthracnose that is being found in the corn fields. I looked at fields yesterday and saw how it is affecting stalk and general plant health. There may be three out of ten plants that have prematurely died because of the disease. When I pushed plants to check stalk strength, these are the ones that break. With the conditions we are experiencing this year, this matter will only get worse. So the question is where does the stalk quality curve cross with the grain moisture curve? Wet corn is better than down corn. The following pictures are examples of what Anthracnose looks like in corn. I hope they will help you identify the problem and act accordingly.
Anthracnose of corn, caused by the fungus Colletotrichum graminicola, is a disease that affects leaves and stalks. Symptoms appear initially on lower leaves as small, oval water-soaked lesions that enlarge and turn tan to brown with yellow to reddish-brown borders. Lesions may coalesce and blight entire leaves. Older lesions will turn gray in the center with small black specks. These fungal structures (acervuli) look like black spines when viewed with a hand lens. Anthracnose leaf blight may be followed by top kill and stalk rot. The leaf blight rarely causes large yield losses; the stalk rot phase is most important.
Symptoms on stalks appear as water-soaked areas on the surface of the lower internodes, that later develop into brownish linear streaks. These streaks turn black later in the season. Larger, oval, black areas may also develop. Pith of infected stalks disintegrates and is gray to dark brown. Severely infected stalks are likely to lodge.
This disease is favored by cool to warm, wet, humid weather, reduced tillage, and stresses that result in early senescence. The fungus overwinters in infected crop residue (leaves, leaf sheaths and stalks) and spores are spread by splashing rain and wind.
Peggy Sellers, Purdue University