Healing From Hail

Don't Assume Fungicides Are Necessary

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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Shredded leaves can send farmers running for the sprayer, but there is no evidence that fungicide applications can improve yields in hail-damaged crops. Fungicides work only on fungal diseases, and those don't require tissue damage such as that created by hail to take hold. (DTN photo by Russ Quinn)

ROCKVILLE, Md. (DTN) -- The most difficult task after hail damage isn't walking through damp fields, assessing shredded leaves or counting snapped plants.

It's doing nothing about it.

"One of the things people are tempted to do is spray fungicides after hail damage, but there's little evidence that it does much to help out," said Matt Montgomery, a sales agronomist with Burrus Seed. "Honestly, the worst part about it is that there's nothing you can do to solve a hail damage problem."

THE FUNGICIDE MYTH

"There is a strong perception that when corn is injured by hail, it is more susceptible to disease," said Ohio State agronomist Peter Thomison. Growers often assume that a fungicide application will pay off in light of this perception, Montgomery said.

It's true that plant wounds can favor certain bacterial diseases, such as Goss's wilt, common smut and stalk rot in corn and bacterial blight and bacterial pustule on soybeans.

But fungicides do not work against bacterial diseases. They only control diseases caused by fungal pathogens, such as northern corn leaf blight, gray leaf spot, eye spot, and common rust on corn, and brown spot and frog eye on soybeans.

These fungal diseases do not require a plant wound to enter a plant, and there isn't good evidence to suggest that hail damage increases the incidence of fungal pathogens, Montgomery said.

University of Kentucky plant pathologist Carl Bradley actually tested the yield response of hail-damaged plants to fungicides in a two-year study. To mimic hail damage, Bradley used a handheld, gasoline-powered string mower to shred 25% to 30% of the leaves in corn plots at the V12 growth stage.

In both years, the fake hail damage did indeed drop yields compared to undamaged control plots. But fungicide applications had no significant effect on yields in both years compared to untreated plots, even though the damaged plots did show more disease in the first year.

"Results from our research trials indicated that foliar fungicides provided very little benefit to corn injured by simulated hail; thus, growers should consider factors other than hail damage when making fungicide application decisions for corn," Bradley concluded in his study.

As always, base fungicide applications on the presence of fungal diseases and favorable disease weather conditions, Montgomery said.

You can find Bradley's study at http://bit.ly/… and a summary of hail research here: http://bit.ly/…

ASSESSING DAMAGE

Most hail damage is harder on the eyes than it is the corn plant, agronomists told DTN. In rare cases, corn will be completely defoliated or snapped. "But in 95% of the cases, the actual yield impact is pretty minor," Burrus agronomist Montgomery said.

Shredded leaves look alarming, but as long as they are below the ear, they aren't actively involved in filling grain. Damage to the stalk is actually more likely to cause yield loss, Montgomery said.

"Look for any damage to the interior of stalk, like chunks taken out of the side that go deeper than just the sheath around the stalk," he advised. "If you see divots carved out of stalk, or bruising of the stalk, then you might have potential issues down the road with standability." Target those fields for early harvest, he advised.

Soybeans are resilient to leaf damage as well and very young plants are most at risk. "When a soybean plant gets a little more mature, it has more targets to hit," Montgomery said. "But there is only one growing point, so if that gets shaved off, you'll have loss of the plant."

Purdue University has a detailed guide to assessing the extent of hail damage and likely yield loss in corn here: http://bit.ly/…

For soybeans, the University of Nebraska guide to assessing hail damage is here: http://bit.ly/…

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com

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(CZ/BAS/AG)

Emily Unglesbee