Risk of ear rot and mycotoxins in hail damaged crops

Risk of ear rot and mycotoxins in hail damaged crops

Since the crop started grain fill, there have been several reports of hail damage to crops. Apart from shredding leaves, hail can bruise ears leaving them at risk for infection by ear mold fungi and consequently mycotoxin contamination.

Past research on the effect of hail damage on ear rot and mycotoxin contamination

On August 9, 2009, over 1 million crop acres in central Iowa were damaged by hail while the corn crop was at R1 to R3. Ear rot severity and mycotoxin severity were significantly greater in hail damaged fields compared to fields that were not damaged by hail¹. Gibberella ear rot was the most prevalent ear rot, likely because conditions were favorable for the mold to develop, that is, cool and wet. Ear rot severity was a good predictor of vomitoxin (deoxynivalenol (DON)) and zearalenone contamination.  Approximately 50 percent of the grain samples from hail-damaged fields were above FDA regulation levels.

Figure 1. Gibberella (pink), Fusarium (white) and Cladosporium (black) ear rots associated with bruising caused by hail damage to corn ears in August 9, 2009. Photo by Alison Robertson, ISU. 

Recommendations for 2026

Some of the corn that has been damaged in 2026 is a little further along in development (R3 to R5) than the corn damaged in 2009. Ear rots may still be a problem, although since they have less time to develop before physiological maturity, they could be less severe. Many ear rots will continue to develop, however, as long as grain moisture is greater than 15%. If you have a corn field that was affected by the recent hail damage, check out these recommendations: 

1. Hail damaged fields should be scouted for ear rots.  Ear rot symptoms may be visible starting three weeks after infection². It is important to recognize which ear rots are present in the field. The Crop Protection Network “An Overview of Ear Rots” is a good resource for recognizing the different ear rots. 
2. While ear rots do not always result in toxin problems, they are a warning sign to suspect toxins.  If more than 10 percent of ears in field are moldy (>25% of the ear), the field should be harvested and the corn dried as soon as possible.
3. If hail-damaged fields are salvaged for silage, mycotoxin contamination may be an issue. Ear rot and mycotoxin accumulation will depend on which pathogen is prevalent and conditions after infection.   Deoxynivalenol was detected 7 to 11, and 11 to 23 days after inoculation (at silking) in a susceptible and moderately resistant hybrid, respectively³. 
4. The best option for moldy grain is to feed or sell it. If feeding, the grain should be tested for mycotoxins. The ISU Veterinary Diagnostic Laboratory can test for mycotoxins.
   1. To collect a grain sample for mycotoxin testing it is best to take a composite sample of at least 10 pounds from a moving grain stream, or to take multiple probes in a grain cart or truck for a composite 10-pound sample. If toxins are present, it is possible that it can be fed to a less sensitive livestock species, such as beef cattle (depending on the specific toxin and its concentration). A veterinarian or extension specialist can help with these decisions. If the grain is sold, there may be a reduced price due to mold damage.  For mycotoxin testing in silage, chopped silage, sampled just before ensiling, is best. 

Literature cited

¹ Robertson A.E. et al. 2011. Effects of natural hail damage on ear rots, mycotoxins, and grain quality characteristics of corn.  https://doi.org/10.2134/agronj2010.0276

² Reid, L. M., and Sinha, R. C. 1998. Maize maturity and the development of Gibberella ear rot symptoms and deoxynivalenol after inoculation. Eur. J. Plant Pathol. 104:147-154.

² Atanasova-Penichon et al. 2012. Chlorogenic acid and maize ear rot resistance: a dynamic study investigating Fusarium graminearum development, deoxynivalenol production, and phenolic acid accumulation. Molecular Plant-Microbe Interactions, 25(12), pp.1605-1616