Making Fungicide Decisions on Hail Damaged Crops

August 11, 2009

By Daren Mueller, Department Plant Pathology

During the past weekend hail storms once again wreaked havoc on corn and soybean fields across Iowa. Much like hail damage last month and last week, growers have an option to spray fungicides to protect remaining leaf tissue. We wrote an article last month walking through a fungicide decision on hail-damaged crops at that point in the growing season. Much of the information in that article remains relevant.

Points to once again consider:

1- There has only been one replicated study completed with the proper checks looking at hail damage on corn. The main conclusions from that two-year study completed in Illinois was that foliar fungicides did not significantly improve yield in either the damaged or non-damaged plots compared to the non-treated controls. Results from this research indicated that foliar fungicides provided very little benefit to corn injured by simulated hail.

2- This late in the season, there is not much time left for additional foliar disease to develop and contribute to yield loss, even with tattered leaves. Many of the diseases that are managed with fungicides do not require the wounds created by hail.

3- Depending on the percent of damage, yield potential is less in hail-damaged crops. Remember that fungicides protect yield, not create more yield. So, if yield potential is lowered by hail, this reduces the chances of recouping your costs of applying a fungicide.

eyespot and hail 2

Hail damage to corn with eyespot, five days after hail storm. Lang, 2009.

Daren Mueller is an extension specialist with responsibilities in the Corn and Soybean Initiative. Mueller at (515) 460-8000 or by emailing

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