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How to evaluate hail damage in corn

Corn Illustrated: Give the crop time to recover before assessing injury.

Tom J. Bechman, Midwest Crops Editor

June 6, 2024

4 Min Read
A close-up of a cornstalk with bruising and damage from hail
WOW! POW! This storm packed a punch. Besides hail, winds were strong enough to take the roof off a tool shed just down the road. Note bruising on the stalk from direct hail hits. This field was a total loss. Photos by Tom J. Bechman

“Hey, my corn was hit by hail last night.” That’s what you tell your crop insurance agent because you have hail insurance. Don’t be surprised if he or she says they’ll be out in a week or even later, especially if the window for replanting is closed. Agronomists say your agent is likely not dodging you. Assessing crop damage claims vs. storm damage to buildings and equipment is a whole different animal.

“You want to give it at least a week so you can judge regrowth and see how the crop is going to recover,” says Justin McMechan, crop protection and crops system specialist at the University of Nebraska. Two weeks would be even more insightful, he notes.

“Growth stage when corn is hit by hail is a big deal,” McMechan says. “Until corn is V5 to V6, the growing point is below the ground. So, in many cases, what happens above the ground doesn’t go a long way toward determining potential yield loss. Damage later in the season can be more serious for corn.”

A cornfield with shredded leaves and damaged stalks from hail

McMechan has studied hail damage on crops intensively. In fact, he uses a hail machine to simulate hail, then studies how quickly the crop recovers. The goal is gaining insight into how much yield potential is lost based on damage at certain stages.

Mark Licht, Extension crop systems specialist for corn and soybean management at Iowa State University, agrees that if the whorl of young plants is intact and new leaves can emerge, losses on young corn may be minimal. “Corn can look beat up and still only suffer minimal yield loss,” he says.

Related:Why V5 corn stage is so important

“The same thing sometimes happens when leaves are tattered, but not totally destroyed, even when plants are bigger,” Licht says. “As long as green tissue is still attached and photosynthesis can occur, leaves often continue to be productive.

“More serious damage occurs when corn approaches reproductive stage. Yield lost can range up to 100% if corn plants are totally defoliated at tasseling.”

Examples: Hail-damaged corn

Here are three scenarios that demonstrate potential yield loss based on degree of defoliation at different stages of growth. Expected yield loss is based on information from National Crop Insurance Services, presented in the 2024 Purdue University Corn and Soybean Field Guide.

1. Hard hit. Suppose corn at the 12-leaf stage is 80% defoliated. That’s an estimated 18% yield hit. If yield potential was 220 bushels per acre, now it’s closer to 180. If the same intensity storm hit seven-leaf corn, yield loss would be closer to 7%, or 15 bushels.

2. Chopped, shredded and diced. The field looks like a war was fought there. Is actual damage as bad as it looks? According to this source, 50% defoliation on that same seven-leaf corn is a 2% loss, or maybe 5 bushels per acre. On 12-leaf corn, expect 9% loss, or 22 bushels, with expected yield just under 200 bushels per acre.

Related:How to assess hail damage in soybeans

3. Tattered leaves. You can tell the field was pelted with hail, but most leaves are still attached. At 20% defoliation, expect seven-leaf corn to fully recover — no yield loss. In fact, 20% defoliation may not cause yield loss unless corn is at the 11-leaf stage. At 12-leaf corn, 1% expected yield loss amounts to just over 2 bushels per acre.

With 80%, 50% and 20% damage at tasseling, the outcome is much bleaker. Expected yield losses are 68%, 31% and 7%, respectively.

Close up of corn plants with tattered leaves from hail

Toward better yield loss estimates

“Information provided by the crop insurance industry is surprisingly accurate,” McMechan says. He has studied hail damage intensively for several years, using hail machines to simulate different degrees of damage and then following plots to yield to document impact.

If you follow the protocol set for hail adjustors, you can arrive at reasonable damage estimates, he says. That includes waiting seven to 14 days before assessing damage and inspecting three areas intensely within the core area. Check another location for every additional 40 acres in the field.

“We have developed a formula to get even closer at predicting actual damage, but it is fairly complex,” McMechan notes. “It’s not a formula we suggest farmers try to use yet.”

However, he believes their work could be useful soon. “With companies developing sophisticated applications for drones, we could see it adopted there,” he says. “It could one day soon help agronomists and scouts really zero in on expected damage from hailstorms.”

Read more about:

HailstormHail Damage

About the Author(s)

Tom J. Bechman

Midwest Crops Editor, Farm Progress

Tom J. Bechman became the Midwest Crops editor at Farm Progress in 2024 after serving as editor of Indiana Prairie Farmer for 23 years. He joined Farm Progress in 1981 as a field editor, first writing stories to help farmers adjust to a difficult harvest after a tough weather year. His goal today is the same — writing stories that help farmers adjust to a changing environment in a profitable manner.

Bechman knows about Indiana agriculture because he grew up on a small dairy farm and worked with young farmers as a vocational agriculture teacher and FFA advisor before joining Farm Progress. He works closely with Purdue University specialists, Indiana Farm Bureau and commodity groups to cover cutting-edge issues affecting farmers. He specializes in writing crop stories with a focus on obtaining the highest and most economical yields possible.

Tom and his wife, Carla, have four children: Allison, Ashley, Daniel and Kayla, plus eight grandchildren. They raise produce for the food pantry and house 4-H animals for the grandkids on their small acreage near Franklin, Ind.

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