Identification and Management of Corn Head Smut
February 1, 2025
Corn head smut is caused by a fungal pathogen (Sphacelotheca reiliana) that systemically infects corn seedlings but does not show symptomology until later in reproductive stages. The disease can be found on the tassel and ear of infected corn plants (Figures 1 and 2). Head smut can sometimes be confused with common smut, which is more commonly found (Figure 2). The major difference between the two is that head smut infects plants systemically while common smut only causes local infection. Unlike common smut, which forms black galls on various plant parts (leaves, stems, and ears), head smut produces thin strands covered in black spores mainly on tassels and ears. Dramatic yield impacts are not commonly reported with head smut due to low disease incidence.
Identification
The fungus infects seedlings shortly after germination, but symptoms are not visible until reproductive stages. It produces thin, wire-like protrusions of the vascular bundles in the tassel and/or thin green protrusions when present on the ear (Figures 1 and 2).1 Infected ears have tear drop shaped husks and the ear is replaced with black teliospores when the husk is opened (Figures 3 and 4).1
Management
The primary source of inoculum for head smut comes from teliospores in the soil. The spores can remain dormant for up to four years.2 The pathogen prefers dry soils and temperatures between 70 and 82 °F.2
The best way to manage head smut is the use of cultural practices that reduce disease inoculum or interrupt the disease triangle. Some of the key strategies may include:
- Seed treatment – treating seeds with appropriate fungicides before planting help protect against early-season infections.
- Crop rotation – avoiding continuous corn planting in the same field can help reduce soil spore levels.
- Cultural practices – planting early can help avoid environmental conditions that favor the fungus. Equipment should be clean of debris when moving from field to field.
- Maintaining a good soil fertility program – head smut can become more serious when the crop is deficient of nitrogen.
Conclusion
- Yield response is variable. However, incidence is typically low across a whole field.
- Mitigating head smut is primarily achieved by preventing early seedling infections with a fungicide seed treatment and mitigating injury from cultivation.
- Seed treatments are a good measure of control since most head smut infections occur early in the season.
- Planting earlier can help avoid the optimal conditions of head smut infections (dry and warm soils).1
- Crop rotation to non-susceptible crops may help reduce future incidence in corn; however, with the long life of the spores in the soil, crop rotation is unlikely to eliminate future infestations.2
Channel Agronomist
Trenton Houston
Sources
1Jackson-Ziems, T. Head Smut. CropWatch. University of Nebraska-Lincoln. https://cropwatch.unl.edu/plant-disease/corn/head-smut/
2Mohan, S.K., Hamm, P.B., Clough, G.H., and duToit, L.J. 2013. Corn smuts. PNW 647. A Pacific Northwest Extension Publication. Oregon State University. https://extension.oregonstate.edu/sites/default/files/documents/pnw647.pdf
Websites verified 12/20/24. 1110_487837
Seed Brands & Traits
Crop Protection
Disclaimer
Always read and follow pesticide label directions, insect resistance management requirements (where applicable), and grain marketing and all other stewardship practices.
©2024 Bayer Group. All rights reserved.