We've had a lot of moisture lately. Although the season should be winding down, late planting has led to later maturing fields this year. This has many producers worried about ear and stalk rots and even seed germinating on the cob. Diplodia ear rot and Fusarium ear rot are our most typical ear rots in a normal year. Both Diplodia and Fusarium also can cause a stalk rot.

Fusarium ear rot, normally the most common ear rot found in Illinois and the Midwest, is characterized by pinkish to salmon colored fungal tissue growing on the kernels. The fungus can be scattered on the cob or, often, seen toward the middle of the ear. The color is distinctive. Fusarium ear rot produces mycotoxins called fumonisins. Fusarium is favored by hot and dry conditions at pollination and high humidity.

Diplodia ear rot is first noticeable in the field by a bleached appearance of the husk. When you peel back the husk, you see a white, fluffy fungus. The good news is that the Diplodia fungus will not produce toxins in the grain; the bad news is that kernels will be very lightweight and shriveled and of very poor quality. Diplodia has been rampant across the mid part of the state this late season.

What is the right moisture to harvest corn that has had fungal ear rot problems? The answer really depends on several important issues. First what ear rot do you have in the field? The second issue is what weather is expected? Ear rot fungi will continue to develop in the field or in storage at above 18% moisture. If dry weather is expected you can try to save some drying costs and leave the grain to dry a bit longer in the field. If you have moderate infection though and wet weather is expected harvesting and drying to at least 18% is probably your best option.

Do you really have to dry it to 18 % moisture? Well, that depends on what you are planning to do with the grain. If you are planning on long term storage actually you should get the moisture down below 15-16%. Diplodia is not your biggest worry for storage but the many species of another of our ear rots, Aspergillus, produce very serious grain toxins such as aflatoxin, and are a concern as they like to grow from about 14-18% moisture.

Diplodia, Fusarium and many other fungi cause stalk rots in our area. They produce symptoms such as white, black or pink stalk discoloration but their main impact is decreased stand-ability of the stalk.

Scouting for stalk rots is a fairly easy endeavor. Evaluate 20 plants at each of 5 locations in a field. Use the common zigzag-scouting pattern to accurately evaluate stalk rot incidence. Begin scouting when the kernels are at 30-40% moisture. You can use either of two methods to evaluate stalk integrity. The first is to lightly grasp the stalk at waist level and push it about 15 degrees from the vertical. A second method is to pinch the base of the stalk below the first node. Stalks that lodge or collapse when pinched should be marked positive for stalk rot. Fields can endure stalk rot incidence up to 10%. However, incidence above 10-15% calls for an early harvest to prevent further damage and lodging. You can investigate the ears for ear rot just by peeling back the husk at the same time you are scouting for stalk rots.