Yesterday and over the previous week, storms caused scattered hail damage in central Wisconsin and short-term flooding in south eastern Wisconsin. Most of the crop was at V7 or less when these storms moved through Wisconsin. We are at the point where there are few planting/replanting options available for corn. We might still be able to plant other crops, but there are few viable good alternatives. The keys to storm related damage of crop fields are to: 1) be patient, 2) determine the crop growth stage, and 3) assess plant health accurately.

After a storm event we need to be patient and let plants respond. Plants can usually survive short periods of flooding of less than 48 hours (Wenkert et al., 1981). Likewise hail damage is minimal on plants less than V7 [Table 1 derived from Vorst (1990)]. Within a few days growth should occur within plant whorls. New leaves will become visible quickly within a couple of days if air temperature is warm. Now is a good time to assess the plant growth stage. Crop insurance damage charts are based upon the stage of crop development, so recording the date of the storm event and the correct stage of development is key to assessing damage. To assess whether the plant is healthy the growing point needs to be observed. Look for color other than a healthy cream or light yellow. The first signs of damage on a growing point are a change to a light red or brown within about 4-6 days. If the growing point changes color, then the plant will likely not yield well and may even die.

To assess plant stands that have been damaged and whether a replant or late-planting may be needed see Corn Replant/Late-Plant Decisions in Wisconsin (UWEX Bulletin A3353).

Table 1. Yield impact of plant leaf defoliation on corn yield at different stages of development.

Literature Cited

Vorst, J.V. 1990. Assessing Hail Damage to Corn. National Corn Handbook NCH-1:4 pp.

Wenkert, W., N.R. Fausey, and H.D. Watters. 1981. Flooding responses in Zea mays L. Plant Soil 62:351-366.