Recent flooding in parts of Ohio, especially the NW counties, has caused major damage to many cornfields. In some river bottoms, corn was immersed up to the tassels.

Since much of the corn was shorter than normal (with low ear height – due to drought conditions), the likelihood that ears were immersed by flood waters was greater. Much of the corn was in the dent stage when flooded. The impact of this flood damage on corn will be highly dependent on kernel stage of development, length of the flooding period, how much of the corn plant was immersed during flooding, and subsequent weather conditions.

Since late season flooding is an uncommon event, little information is available on its effects on corn at this stage of kernel development, and how to best salvage damaged corn. A major concern is the impact of flooding on grain and silage quality. In past reports, when corn in the dent stage was covered by flood water for six hours or more and nearly completely caked with mud for up to two weeks, damage from ear rots and premature kernel sprouting was extensive in those areas of fields where water had covered the ears the longest. Although such damage may be negligible in fields where water never covered the ears, prolonged flooding may cause significant injury to the roots, if not premature root death. Such plants will be more vulnerable to stalk rots thereby increasing the likelihood of stalk lodging, especially if harvesting is delayed. Therefore, as soon as plants have dried, stalks should be inspected to determine the degree of rot. If rot is extensive, these affected fields should be harvested first to minimize further yield loss.

Another issue that may impact injury from immersion is whether ears were in an upright or downward position when flooded. If most plants had not yet reached black layer when flooding occurred, most ears were probably in an upright position which would probably result in ears catching and retaining more soil, etc. Corn growers in the South have observed that once the ears are soaked from flooding, they quickly rot at high temperatures so prompt harvesting is necessary. Moreover, soaked ears are often associated with premature kernel sprouting, which can lead to secondary bird damage and insect feeding, especially if husks are loose.

The combined effects of excess moisture, bird and insect damage and warm temperatures may also result in ears being colonized by mycotoxin producing molds. In general, mold development and ear rots are of greater concern when favorable weather occurs during silk development, however, fungi may also infect and cause ear rot late in the season, especially if ears remain in an upright position and accumulate soil and moisture. Normally, healthy, intact kernels at the dent growth stage are not easily infected by fungi, however, these same kernels softened by excess moisture and damaged by birds become easy targets for both saprophytic fungi (and bacteria) and ear rots, most of which are present in soil particles and debris found in flood waters. Samples of grain harvested from flooded fields, especially if ears were covered with flood water for extended periods or plants were lodged, should be sent for toxin analysis before feeding grain to animals. Laboratories for mycotoxin analysis can be found on the Ohio Field Crop Disease web site.

When dealing with flood damaged corn, a common suggestion is to allow rains to wash off as much soil as possible before harvesting. Another observation is that flooding often deposits considerable debris on fields making harvesting difficult, as will dust associated with soiled plants.

For more information on salvaging corn damaged by late season floods, consult the Penn State Corn and Soybean Management website – Managing Flood Damaged Crops.

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