Fusarium Crown Rot in Corn
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Crop Focus
Written by Mark Jeschke, Ph.D., Pioneer Agronomy Manager
Key Points
- Crown rot is a fungal infection of corn that occurs at the base of the stalk near the soil line.
- Crown rot of corn is commonly attributed to pathogens in the Fusarium genus, although the exact species or complex of species that cause it has yet to be determined.
- Much remains unknown about crown rot and research is ongoing to determine the casual organism(s), timing of infection in corn, environmental conditions favorable to infection, and effective management practices.
Crown Rot in Corn
- Crown rot is a form of fungal infection in corn that affects corn plants at the base of the stalk near the soil line, where the fungus infects the root and stalk tissue.
- Crown rot has been observed in corn plants for years, but it seems to have increased in severity and frequency in recent growing seasons.
- Infection of the plant occurs early in the season, but symptoms often do not become apparent until mid-season or, more commonly, when corn is nearing maturity.
What is the Crown on a Corn Plant?
- The term crown refers to the base of the corn stalk where the nodal roots connect to the stalk.
- The crown is the nexus between the root system and the aboveground portion of the plant, which means that the health of the crown is critical to the health of the plant.
Causal Pathogen
- There is much that remains unknown about factors leading to crown rot in corn, including the exact pathogen or complex of pathogens that cause it.
- Root and crown rots developing in corn after the seedling stage are most commonly associated with Fusarium species, although other pathogens such as Rhizoctonia solani and Pythium spp. have been associated with crown rot in some cases.
- Fusarium is a large and diverse genus that includes numerous species that are ubiquitous in agricultural soils and several species known to be pathogens of corn.
- Research in South Dakota showed eight different Fusarium species capable of causing root rot in corn (Okello et al., 2019).
Figure 1. Split corn stalk showing infection in the crown and root tissue.
Symptoms
- Symptoms of crown rot in corn include stunted growth, wilting, and discoloration of the lower leaves resulting from the infection of vascular tissue in the crown.
- Visual symptoms often become apparent as the field nears maturity when individual plants will begin change color and senesce early. Affected plants will often be surrounded by healthy plants.
- Digging up affected plants and splitting the stalks will reveal dark discoloration of the crown tissue.
- As the disease progresses, the lower stalk may become discolored and rotted, and the plant may die prematurely.
- Infection can extend out into the roots or upwards in the stalk.
Similar Diseases
- Red root rot (Phoma terrestris) can cause symptoms similar to those of crown rot and may appear in the same fields. Deep red to purple discoloration of crown and root tissues are associated with red root rot but may also occur with crown rot.
- Physoderma maydis can cause stalk rot near the base of the plant that may appear similar to crown rot. However, plants infected with Physoderma stalk rot will often appear otherwise healthy, with the main threat to yield coming from stalk lodging.
Figure 2. Crown rot of corn in a mature corn plant.
Favorable Conditions
- It is difficult to identify specific environmental conditions that favor crown rot infection and development since it is not yet known precisely when infection leading to crown rot takes place.
- Cold and wet conditions early in the season are generally favorable for infection by soil-borne pathogens – wet soils favor fungal organisms and cold temperatures stress the plant, reducing its ability to fight off infection.
- The 2022 growing season was characterized by an extended cold period during April and early May in much of the Midwest – incidence of crown rot appeared to be more common in fields that were planted early and experienced early-season cold stress.
- Crown rot can be more common in areas with heavy soil and poor drainage, although it has been observed in a variety of soil conditions.
- Field observations suggest that cold and wet conditions early followed by hot and dry conditions later in the season may be particularly favorable for crown rot development
- Heavy manure applications have been associated with higher incidence of crown rot in corn.
- Infection can be exacerbated by injury to the roots or crown, such as that caused by insect feeding.
Yield Impact and Management
- Crown rot can reduce yield and increase the risk of lodging in affected plants.
- Plants that die prematurely due to crown rot can have lower yield due to reductions in kernel number and weight.
- Research on management practices for control of crown rot has been limited thus far due to the lack of an inoculation assay for inducing crown rot infection.
- Management recommendations are largely anecdotal at this point, based on opportunistic observations in fields where natural crown rot infection was present.
Fungicides
- Fungicide Seed Treatments: Fungicide seed treatments protect against Fusarium species for up to six weeks after planting, but activity does not persist long enough to protect against infection occurring beyond the seedling stage.
- In-Furrow Fungicides: Research on the use of in-furrow fungicides for control of crown rot is ongoing, but so far has not shown a consistent benefit.
- V5-V6 Foliar Fungicides: Early foliar fungicide applications are also being evaluated for crown rot control but have not shown a consistent benefit.
- It seems unlikely that a foliar fungicide application could be effective against crown rot. Foliar fungicides are translocated in the xylem tissue, which means they can only move upward in the plant and are unable to translocate to the base of the plant where crown rot infection occurs.
Other Management Considerations
- Susceptibility to crown rot infection appears to vary among corn hybrids, but no hybrid ratings are currently available.
- Management practices that reduce insect feeding to the roots will help reduce susceptibility to infection as well as support the overall health of the plant and its ability to fight off infection.
- Research is underway to explore possible impacts of corn nematode injury on crown rot occurrence.
- In general, management practices that reduce stress to the corn plant will help improve its resilience against infection by fungal pathogens.
References
- Byamukama, E. and F. Mathew. 2022. Fusarium Root and Crown Rot Developing in Corn. S. Dakota State Univ. Ext.
- Okello, P.N., K. Petrovic, B. Kontz, and F.M. Mathew. 2019. Eight Species of Fusarium Cause Root Rot of Corn (Zea mays) in South Dakota. Plant Health Progress. 20:38-43.
- Robertson, A., K. Wise, and T.A. Jackson-Ziems. 2023. Frequently asked Questions about Crown Rot in Corn. Crop Protection Network CPN-2020. DOI: doi.org/10.31274/cpn-20230307-0
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