Thunderstorms pounded across Iowa on June 9, and in addition to the heavy rainfall, hail struck some fields pretty hard in this young 2011 growing season. The next day, on June 10, the corn was looking pretty ragged in the hail-hit fields. Mostly, the hail shredded the corn leaves but some of the stalks have bruise marks and cuts, which can allow disease organisms to enter and eventaully weaken the stalks.
Farmers are being advised by agronomists to assess the damage carefully during the next few days, and not to panic, as corn at this early growth stage can shoot new leaves and recover, as long as the growing point isn't damaged.
The National Weather Service reports rainfall totals ranging from 4 to 6 inches in much of central Iowa during the 24 hour period ending early in the morning of June 10. The heaviest rain fell in the counties south of Des Moines. A farmer reported getting 8 inches of rain in Madison County, southwest of Des Moines.
If the growing point isn't damaged, corn can recover from hail
The severe hail that accompanied some of the thunderstorms have farmers wondering what this will mean for corn yields in these fields. Most of the Iowa corn crop is now in the V2 to V9 stage of growth.
"The growing point in the corn plant is still underground for corn plants at the V6 stage of growth (sixth leaf stage) and younger," says Roger Elmore, Iowa State University Extension agronomist. "This fact helps the plants survive early-season hail events even if the leaves are totally destroyed. The plant will continue to shoot new leaves and continue growing."
Heat unit accumulation for May 1 planting dates are currently hovering slightly above average (107% of the average statewide) indicating that Iowa's crop progress is back on track this year, thanks to the recent warm weather. Elmore says corn development across the state probably ranges from about V2 to V9 (second to ninth leaf stages) thanks to the wide range of planting dates this year. For a more in-depth explanation on what those ranges are, you can order the new ISU publication on corn growth and development.
Don't rush to judgement if your corn field has hail damage
"Be patient if your field has hail damage," advises Elmore. "The short-term weather forecast for warm and sunny weather plus the moisture received from the storms should encourage rapid and healthy regrowth. Corn plants V6 and younger should survive. Assess the more developed plants carefully."
For more detailed information on how to evaluate hail damaged corn, read the ICM News article on assessing hail injury in corn, hail injury on corn, and assessing corn stands for replanting. Also, you can read the replant checklist from the ISU Extension Corn Production website; and a University of Nebraska article on evaluating hail damage to corn.
One last thought: Be aware that hail industry corn staging systems differ from the leaf collar system most university researchers and extension crop specialists use. Table 2 in the new ISU Corn Growth and Development publication that is refereced in this article provides a comparison, notes Elmore.
In brief, the "horizontal leaf" method used by the hail industry is about 1 to 2 stages ahead of the leaf collar system from V2 to V8, he explains. That means a V8 plant in the leaf collar system is similar to a V10 plant in the horizontal leaf system. This is important when you use tables like those included in the University of Nebraska publication that is referenced in this article.
For more information on hail damage and other corn management issues, see the ISU Extension Corn Production Website. Look in the "Image Gallery" under "Crop Diagnostics" for images of damaged corn from previous hail events.