Does it pay spray fungicide on corn or soybeans damaged by hail? Dakota Farmer asked Connie Strunk, South Dakota State University field plant pathologist, if it was a good idea. Here’s her reply:

“A fungicide application cannot recover crop yield potential lost due to hail damage. Fungicides can only protect the current crop yield potential by reducing disease.

“Many of the diseases that are favored by wounding are not controlled with foliar fungicides. Diseases typically found in corn after a hail event include Goss’s wilt and blight, common smut, and stalk rot. Wounding favors bacterial blight and bacterial pustule in soybeans. Fungicides are not effective against the pathogens which cause these diseases.

“Fungicides are used to manage and control foliar diseases such as gray leaf spot, northern corn leaf blight, eye spot and common rust on corn, and brown spot and frog eye on soybeans. These foliar diseases are caused by pathogens that do not require wounds for infection. The yield response to fungicides will be influenced by these foliar diseases more so than hail damage.”

“Research done at Iowa State University utilized a PTO-powered ice-applicator to stimulate hail events on soybeans and then evaluated the effects of applications of Headline fungicide (among other treatments). Mean data from six different trials showed that the fungicide application had no statistical benefit.

“A hail simulation study on corn used different techniques, such as weed-whip damage to simulate hail found the same results. This hail simulation study was conducted by the University of Illinois where the fungicide applications of Headline and Quadris did not result in statistically different yields compared to the non-treated checks.

“Applying fungicides on hail-damaged plants is only warranted if there are significant fungal diseases developing on these plants resulting in yield loss. Fungicides protect the yield potential of plants if significant diseases are present, but they do not improve the yield potential of the crop which was lost to hail.”

For more information, contact Strunk at [email protected] or 605-782-3290.