Effect of Late-Season Hail on Corn and Soybean

As has been common this season, severe weather over the last several days has brought wind and hail to parts of Iowa. This article will address some of the concerns associated with late-season hail on crops.

While contacting your crop insurance agent as soon as you are aware of the hail damage is the first priority, waiting approximately 7 days after the hail event to actually evaluate damage allows for easier differentiation between dead and living tissue at this point in the growing season. Most corn and soybean are somewhere between R2 and R4 growth stage. Corn will have no opportunity to recover lost leaf area or damaged kernels at this point in the season, while soybean has some limited ability to continue producing flowers and leaves, depending on the growth stage.

Corn: Hail to corn in reproductive stages can result in stand loss, defoliation, stalk bruising, and ear injury. At tassel, corn is most susceptible to yield loss, and it becomes less susceptible as the ear matures. Loss of 50% of leaf area at R3 (milk) would be associated with nearly 20% loss in corn yield. Monitor stands carefully for the development of stalk and ear rots that could result in crop lodging and grain quality issues. Damaged grain will be at increased risk of mycotoxin development.

Read more on hail damage evaluations in late-season corn: 

• Iowa State University IPM 78: Hail on Corn in Iowa
• Crop Protection Network Publication CPN-2001 “Ear Rots”
• Crop Protection Network Publication CPN-2002 “Mycotoxin FAQs”
• Crop Protection Network Publication CPN-2004 “Storing Mycotoxin-Affected Grain”

Soybean: Soybean increases in vulnerability to hail damage as reproductive growth stages advance through R5 (Figure 2). Soybean yield loss comes from a combination of stand loss, stem breakage, defoliation, and pod loss. At R3 (early pod), 50% loss of leaf area correlates to less than 10% yield loss in soybean, while node loss results in more significant yield loss. In addition to yield loss associated with plant damage, grain quality may be compromised due to severe plant damage or direct injury to pods. Harvested soybeans may have smaller seed, foreign material in grain, discolored seed from bruised pods, low seed protein, and a limited storage life. Plants in the field may have a longer timeframe of maturation and overall faster plant drydown.

Read more on hail damage evaluations in late-season soybean in the ISU publication: IPM 79: Hail on Soybean in Iowa.

Forages:  For those with hail damage to forage crops like alfalfa or red clover, Dan Undersander and Dan Wiersma at the University of Wisconsin explain how to evaluate the damage in the resource “How to manage hail damaged alfalfa and red clover.”

Late-season weed pressure in hail damaged crops:  The loss of significant leaf area will allow more sunlight to the soil surface; this combined with the recent rainfall creates an ideal environment for flushes of late-season weeds. An article from the University of Nebraska addresses some thoughts on weed management considerations after a hail event. Read more here.

Fungicide-use on hail damaged crops:  Most foliar fungal diseases do not require wounding to infect the plant, but fungicides do require healthy leaf tissue to absorb the product. We are unaware of any research evaluating the effect of foliar fungicide on the development of ear rots in hail-damaged corn, but this is something that could be tested with an on-farm trial this year. Please reach out to your local extension field agronomist if you’re interested in assistance with this kind of trial.