May 25, 2012

Hail storms with quarter- to golf ball-sized hail hit corn, soybean, and wheat fields in several areas of Nebraska this week. At this point in the season, replanting may be an option, but is it the right option for your field? Several UNL Extension resources are available to help you assess crop damage at various growth stages and determine your management options. Consult these resources if you're assessing recent damage of if hail strikes your farm in the coming weeks.

Yield loss data in these publications is based on information from the National Crop Insurance Agency.

Evaluating Hail Damage to Corn, UNL EC126, discusses the three types of hail damage affecting corn -- plant stand reduction, direct damage, and leaf defoliation -- discusses how to estimate yield loss, and describes remedial actions for hailed fields. Being able to determine corn growth stage and accurately estimate the amount of defoliation are essential to accurately assessing hail loss. Until the V6 growth stage, losses from leaf defoliation are usually minor with most loss occurring from stand reduction. At the V6 growth stage the growing point breaks the soil surface and the potential for unrecoverable damage increases. With a mid season hybrid it takes about 475 growing degree days (GDD) to reach V6. A check of accumulated GDD at several Nebraska sites indicates that fields are apt to be near this growth stage. (See GDD tables in the CropWatch Weather section.) While hailed corn plants at the current growth stage can look seriously ugly, the long-term damage and potential yield loss may be less than would occur from replanting now. Even at the 7-leaf to 9-leaf stages, 50% of leaf area can be destroyed and cause only 5% yield loss.

It can be difficult to distinguish living from dead tissue immediately after a storm, so delaying your assessment seven to 10 days can provide a more accurate picture. Another reason for delaying assessment is that some plants initially surviving a storm may soon die becaue of disease infection entering at the sites of plant or stalk damage.

The June 2011 CropWatch article, Assessing Flood/Hail Damage to Crops and Remedial Actions, discusses why it’s also important to consider weed, disease, and insect pressures and includes a table of yields from a research study looking at the agronomic performance of short season corn hybrids planted mid- to late-June.

Evaluating Hail Damage to Grain Sorghum, UNL EC129, describes procedures used to assess sorghum hail damage and may be useful in estimateing crop yields wherever stand loss or defoloiation occurs. Yield loss predictions are based on two factors: 1) stage of growth at the time of damage, and 2) the degree of either direct or defoliation plant damage. Includes guide to determining crop

Evaluating Hail Damage to Soybeans, UNL EC128, describes procedures used to assess soybean hail damage. It may be useful in estimating crop yields from stand reduction, leaf defoliation, stem damage, and pod damage. Includes guide to determining crop growth stage.