Gibberella Ear Rot and Stalk Rot in Corn

Gibberella stalk rot and ear rot are caused by the fungus Gibberella zeae, the same pathogen that causes head scab of wheat (Fusarium graminearum). The fungus overwinters on corn and wheat residue. This pathogen produces mycotoxins in corn and wheat, including deoxynivalenol (DON, also called vomitoxin).

What to Watch For

Gibberella ear rot occurs in corn when Gibberella zeae enters developing kernels through the silks. Cool, wet weather during and after silking increases the chance of the disease infecting and colonizing ears.¹ Wounds from birds or insects can also create openings for the disease to enter ears.

Once infected, the kernels develop mold, which often moves from the tip to the base of the ear. Severely infected ears can look mummified when the ear husk and cob fuse together. Mold color can begin as white, but turns a characteristically dark-red or pink color (Figure 1).²

Gibberella stalk rot infects stalks following pollination via wounds in the stalk and through the roots, causing the lower stalk to soften and turn straw-colored as plants die. Pith tissue disintegrates, leaving the vascular strands intact. The inside of a rotted stalk has a pink to red discoloration (Figure 2). Small, blue-black fungal bodies called perithecia form on the surface of the lower stalk and can be easily scraped off. Spores are produced during wet weather and can be spread by wind and rain splash.

Perithecia are produced between temperatures of 41 to 86 °F and relative humidity ranging from 75.5% to 100%. However, they do not mature and produce spores until temperatures are between 68 to 77 °F with relative humidity between 85% and 100%.³ The spores can be spread by air or rain splash.

Impact on Corn

High yield scenarios favor Gibberella development; however, there are differences between corn products in their susceptibility to the disease. The timing of silking, weather, and insect pressure can influence disease pressure. Therefore, there will likely be field to field variability in disease pressure.

Stalk quality is compromised when Gibberella infects stalks, and early harvest may be necessary when there is substantial lodging potential. Conducting a push test can help determine if stalk rots are likely to cause lodging, requiring early harvest. A push test is done by pushing corn stalks to a 30-degree angle from vertical at eye level. A stalk fails the push test if it does not spring back to upright when released.⁴

Deoxynivalenol (DON or vomitoxin) levels in grain can reduce feed quality and prices at grain terminals. A mycotoxin test can be used to check DON levels in harvested grain and in corn intended for use as silage. DON levels should be 10 parts per million (ppm) or less for beef and feedlot cattle older than four months. DON levels should be no more than 5 ppm for swine, young calves, and dairy animals.⁵ Mycotoxins are concentrated in the dust and lighter, shriveled kernels, so contaminated grains should be cleaned to remove these fine particles.

Management Options

Corn Product – Researchers have identified two types of resistance to Gibberella rots: silk resistance and kernel resistance. Silk resistance may help protect against the fungus growing rapidly down the silk to the kernels. Kernel resistance helps prevent the fungus from spreading kernel to kernel.⁶ Characteristics that resist animal and insect damage are also desirable. Different corn products are likely to have different silking dates, and silking dates aligned with stormy humid weather increase the risk of infection.

Insect Protection – European corn borer (ECB), western bean cutworm (WBC), and corn earworm (CEW) are insects that feed on kernels, opening ears to infection. Traits protecting against these ear-feeding caterpillars should be selected when planting into a field with previous heavy pressure from Gibberella rots or Fusarium head blight.

Fungicide – Fungicide application can help protect silks from infection. Application should occur between silk emergence (R1) and brown silk (R2) stages. Bayer’s Proline^® 480 SC fungicide is an option to help manage Gibberella ear rot. Always use fungicides according to label directions as some fungicides can increase toxin levels if applied at the wrong time.

Combine Adjustments to Reduce DON – When Gibberella rot is more limited to ear tips, the affected smaller and lighter kernels can be blown out of the combine and left in fields using the following adjustments:

• Replace doors with screens on bottoms of clean grain and return elevators. The bottom door can be taken completely off to leave light, infected kernels in the field.
• Add a screen on the unload auger if possible.
• Set the concave wide with the rotor/cylinder speed set slow.
• Close the back portion of the chaffer (sieve) to increase the wind blast, forcing additional light kernels out the returns and over the back of the sieve. Some good kernels may be lost; however, this loss may be acceptable for fields with high DON levels.⁷

Fall Field Work – Fall tillage in combination with shredding plant debris may help assist in plant residue breakdown, reducing inoculum.

Sources

¹Willyerd, K.T., Paul, P.A., and Thomison, P. 2010. Gibberella ear rot and mycotoxins in corn: Sampling, testing, and storage. Ohio State University Extension. PLPATH-CER-04. https://ohioline.osu.edu/factsheet/plpath-cer-04

²OMAFRA. 2024. Identifying corn moulds. https://www.ontario.ca/page/identifying-corn-moulds

³Manstretta, V. and Rossi, V. 2015. Effects of temperature and moisture on development of Fusarium graminearum perithecia in maize stalk residues. Plant Microbiology. 82(1):184–191. https://doi.org/10.1128/AEM.02436-15

⁴Freije, A., Wise, K., and Nielsen, B. 2016. Diseases of corn: Stalk rots. Purdue Extension. BP-89-W. https://www.extension.purdue.edu/extmedia/BP/BP-89-W.pdf

⁵Government of Canada. 2024. RG-8 Regulatory Guidance: Contaminants in feed. Canada Food Inspection Agency. https://inspection.canada.ca/en/animal-health/livestock-feeds/regulatory-guidance/rg-8

⁶Ali, M.L, Taylor, J.H, Jie, L., Sun, G., William, M., Kasha, K.J., Reid, L.M., Pauls, K.P. 2005. Molecular mappings of QTLs for resistance to Gibberella ear rot, in corn, caused by Fusarium graminearum. Genome. 48(3): 521–33. https://doi.org/10.1139/g05-014

⁷RealAgriculture Agronomy Team. 2018. Corn school: Fine tuning the combine to reduce DON levels. RealAgriculture. https://www.realagriculture.com/2018/11/corn-school-fine-tuning-your-combine-to-reduce-don-levels/

Web sources verified 01/22/25. 1211_146682