• Hail adjusters use tables to help evaluate extent of hail damage.  (With insured crops, hail adjusters have the final word.  It is best to let them do their job before offering another opinion.) 
  
• Wait 7-10 days to assess hail damage to corn and soybeans.
  
• Most hail damage to soybeans is as a result of loss of plants to the stand. Soybean populations, as low as 75,000 plants per acre, may be worth saving.
  
• Bruising and freeze injury may cause delayed damage to soybeans. 
  
• Fungicides have questionable benefit with hail damage. Applications should be delayed until leaf tissue regrows.

Once all necessary information has been gathered for the hail-damaged field and the crop has been evaluated for growth stage and surviving population, some decisions can be made concerning appropriate management steps for the hail damaged crop. Hail adjusters use tables to help determine potential losses from hail damage. Two of these tables are featured in the National Corn Handbook NCH-1 chapter “Assessing Hail Damage to Corn.”  One table in this publication offers yield loss estimates for stand loss, and the second table offers yield loss estimates for corn defoliation.  [Note: Hail adjusters usually use the droopy leaf method for corn growth staging. This method adds about one leaf to the stated growth stage, compared to the leaf collar method.]

In general, corn from emergence to about the V7 growth stage can withstand severe hail injury and still recover. This is because the growing point is underground until corn gets to between the V4 and the V6 growing stage and the growing point is protected in the center of the stem. However, direct hits on V6-V7 corn plants by large hailstones can result in injury too severe for the plant to recover. From V7 through reproductive stages, leaf damage and defoliation are the primary sources of yield loss. During ear formation and fill, bruising and damage to the ear must also be considered. The extent of damage to affected plants can only be determined through careful examination at least 7-10 days following the hail event. The 7-10 day time interval is necessary because it takes this long to differentiate living and dead (or diseased) plant tissue. In some cases plant tissue, which appears firm and healthy immediately following the hail event, may decline in health over time.

Stalk bruising was reported from corn following the recent storms. Hail bruising injury to the corn stalk is often superficial, penetrating only through the leaf sheath. Take the time to dissect stalks to get an inside look at the extent of bruising injury. Injury that penetrates deeply into the stalk may interfere with physiological processes in the corn plant.

Soybean defoliation demonstrations suggest that soybeans have a remarkable ability to recover following loss of all leaves, as long as terminal or axial buds survive without injury. However, these demonstrations also show that recovery of the injured soybean plant may become slower and increasingly inconsistent as the plants grow in size. Survival of any leaf tissue, even if the leaves are shredded, will encourage regrowth. The University of Nebraska, Lincoln has an excellent guide to evaluating hail damage to soybeans (Extension Publication EC128 ). As with corn, it is necessary to wait 7-10 days following the hail event in order to accurately evaluate extent of injury to plant tissue. Most yield loss from hail damage to soybeans is as a result of loss of plants to the stand.

Soybeans, which are broken off below the cotyledonary node, will not recover. Bruising is another injury to look for when evaluating hail injury to soybeans. In some cases, bruised plants will recover, only to experience stem breakage or disease later on. Soybean plant populations as low as 75,000 plants per acre may be worth saving, particularly if nearing the latest practical soybean planting date for your area. (Weed control will be a greater challenge than usual.) If hailstones sit against a soybean plant, deep tissue freeze injury may occur. This is a hidden form of injury that can only be assessed over time. 

Fungicide suppliers often recommend fungicide application on hail damaged crops. However, university research suggests that there is little benefit to this practice. Nevertheless, some individuals have reported positive results from fungicides on hail-damaged crops. While fungicides may help protect hail-injured plants, it is necessary to wait for some recovery of leaf tissue prior to fungicide application. Fungicides are absorbed through the leaves. Fungicide application immediately after the hail event could result in most of the product hitting the soil instead of the plant and could be a waste of the product if there is little viable leaf tissue present.

Storm damage and splashing of soil onto plants may result in bacterial infections. One of the bacterial diseases, Goss’s wilt in corn is spread by conditions we recently experienced. Bacterial blight and bacterial pustule can also be expected to show up in soybeans following storms.  Bacterial diseases do not respond to fungicide applications.

Moderate Hail Injury to V10 Stage Corn - Recovery Potential, Good

Hail Bruises on Corn Stalk - Image: Tim Laatsch

Storm Injury to Soybeans - Image: Dr. David Powell