An Overview of Corn Stunt

Introduction

Corn stunt, caused by pathogens transmitted by the corn leafhopper, Dalbulus maidis (Hemiptera: Cicadellidae), has been a major constraint to corn production in Central and South America, particularly in Brazil, where disease outbreaks have occurred recurrently since 2015. In 2024, corn stunt has re-emerged across important corn-producing regions of the South and South-Central U.S., with substantial economic losses documented in Texas, Oklahoma, Missouri, and Kansas.

Corn stunt is caused by a complex of four pathogens, including two bacteria and two viruses, which may occur individually or in combination within infected plants. The bacterial pathogens include corn stunt spiroplasma (Spiroplasma kunkelii) (CSS) and maize bushy stunt phytoplasma (‘Candidatus Phytoplasma asteris’, subgroup 16SrI-B) (MBSP). The viral pathogens are maize rayado fino virus (MRFV) and maize striate mosaic virus (MSMV). CSS, MBSP, and MRFV have all been reported in the U.S. In contrast, MSMV has only been reported in association with corn stunt symptoms in Brazil and Argentina. 

Maps summarizing the distribution of the corn leafhopper and corn stunt pathogens detected in corn tissue samples across the contiguous U.S. are available. To date, the corn leafhopper is the only confirmed insect vector known to acquire and transmit the pathogens associated with the corn stunt disease complex to corn plants in nature.

Symptoms and Signs

Symptoms of corn stunt vary depending on the corn hybrid, corn growth stage at the time of infection, environmental conditions, and the combination of pathogens involved. In general, symptoms are more severe when plants are infected from emergence (VE) to tassel (VT). Common symptoms associated with corn stunt include chlorotic striping or yellow streaks along leaf veins; reddening or purpling of leaf margins, veins, and midribs (Figure 1); and yellowing of the leaf margins and midribs (Figure 2). These symptoms are typically observed in the upper canopy, as corn stunt pathogens are systemic and tend to accumulate in actively growing tissues, particularly in young leaves. Additional common symptoms include stunting and shortened internodes (Figure 3); excessive tillering or ear production (Figure 4); reduced ear size, shriveled or missing kernels (Figure 5); and premature plant decline or senescence. Plants infected with corn stunt pathogens often have fewer, loosely attached kernels compared to healthy ears (Figure 5), which can contribute to greater yield losses and increased volunteer corn in the field after harvest.

Corn stunt-infected plants may exhibit a "zombie plant" appearance (also referred to as the “stay-green” effect), remaining green and physiologically active late into the season while failing to progress normally through reproductive development (Figure 6). This phenomenon results in plants that persist in the field after healthy plants have senesced and reached harvest maturity, delaying or interfering with harvest and increasing handling (drying) costs. In some cases, infected corn plants may also produce adventitious roots from the brace root nodes (Figure 7). In sweet corn, chlorosis and leaf reddening can occur together on the same plants (Figure 8). Because the insect vector begins infesting corn plantings along field margins, symptomatic plants often first appear along field borders and may also occur in patches or irregular patterns throughout the field. In general, corn stunt symptoms begin to develop approximately 3–4 weeks after pathogen(s) transmission.

Disease Cycle

The pathogens that cause corn stunt are obligate parasites, meaning they cannot survive or complete their life cycle without a living host. These hosts include grain corn, sweet corn, and related species of Zea L., such as teosinte. Similarly, the insect vector only reproduces and completes its life cycle on corn and closely related species. Although the corn leafhopper cannot reproduce on other hosts, it may survive prolonged periods by feeding on grass species, such as gamagrass and johnsongrass.

The corn stunt pathogens can be transmitted individually or in combination from plant to plant by the feeding of corn leafhoppers. The insect vector acquires the pathogens while feeding on the phloem of infected corn plants. After entering the corn leafhopper’s body, the pathogens undergo an incubation period during which they multiply within the insect. Following this incubation period, the pathogens reach the insect’s salivary glands and are transmitted to healthy corn plants. Although the corn leafhopper acquires corn stunt pathogens by feeding on infected plants, it cannot immediately transmit them to healthy plants. The pathogens must first circulate and multiply within the insect and reach its salivary glands before transmission can occur.

Once transmitted to corn plants, corn stunt pathogens colonize parts of the phloem. Then, the infected plant may serve as an inoculum source for additional corn leafhoppers. The average duration of each stage, including pathogen acquisition by the insect vector, incubation within the vector, transmission into the plant, and incubation within the plant, is illustrated in Figure 9.

Corn stunt pathogens are not transmitted from adult corn leafhoppers to their offspring. Therefore, both nymphs and adults must acquire the pathogens by feeding on infected corn plants in each generation to become capable of transmitting them.

Yield Losses and Impact

In 2024, corn stunt re-emerged as an important disease problem, with outbreaks reported in corn fields across Missouri, Oklahoma, and Texas. Yield losses due to corn stunt were estimated to be 14.1 million bushels in Texas and 6.9 million bushels in Oklahoma. Missouri also experienced losses attributed to corn stunt, but to a much lesser extent (4,767 bushels). In 2025, the corn leafhopper was detected in several southern U.S. states, but populations were substantially lower than those observed during the 2024 outbreak. Consequently, no significant yield losses due to corn stunt were reported.

Although corn stunt gained attention in 2024, the disease is not new to the U.S. The disease was first reported in 1945 in the Rio Grande Valley of Texas. A major outbreak also occurred in southern Florida in 1979 and 1980 following Hurricane David, resulting in estimated economic losses of up to $60 million in hybrid seed production and breeding nurseries.

Diagnosis

Diagnosis of corn stunt is based on a combination of field symptoms, the presence of corn leafhoppers, and laboratory confirmation of the pathogens involved. Because symptoms may vary depending on the corn hybrid, environmental conditions, the plant growth stage at infection, and the pathogen or combination of pathogens infecting the corn plants, accurate diagnosis based on visual symptoms can be challenging. In addition, since several pathogens usually occur together in infected plants and produce similar disease symptoms, laboratory testing is necessary to confirm the presence of corn stunt pathogens. For the most reliable diagnosis, samples should be collected from plants that have recently exhibited symptoms of corn stunt. Leaf tissue collected near the base of symptomatic leaves, especially from the midrib region, is commonly used for pathogen detection. Proper sample handling and storage are important to preserve pathogen integrity prior to laboratory analysis, so check with a diagnostic laboratory before submitting samples to ensure optimal sampling methods.

If you suspect that your corn field is showing symptoms of corn stunt, collect one to three complete leaves, including the leaf collar, from randomly selected symptomatic plants that have not yet reached senescence. Using clean scissors, remove the upper portion of each leaf and retain the lower 6–8 inches (15–20 cm), including the leaf collar. Place the leaf sections in a sealed plastic bag with a dry paper towel to absorb excess moisture. Keep the samples refrigerated (do not freeze) and submit them to a diagnostic laboratory as soon as possible, preferably by overnight shipping. One laboratory that offers testing for corn stunt pathogens is the Plant Disease and Insect Diagnostic Laboratory (PDIDL) at Oklahoma State University.

Disease and other conditions that appear similar to corn stunt

Visual symptoms alone are insufficient to confirm corn stunt, as several nutrient deficiencies, herbicide injuries, environmental stresses, and other diseases may produce similar symptoms.

High Plains Wheat Mosaic Virus

This disease, commonly known as the High Plains Disease (HPD), is caused by the High Plains wheat mosaic virus (HPWMoV) and infects corn and wheat. Symptoms of HPD on corn include stunting, mosaic, and yellowing (Figure 10). Long red longitudinal stripes can also be associated with HPD.

How to distinguish HPD from Corn stunt: Symptoms often include distinct chlorotic or white streaks and are commonly associated with nearby wheat or volunteer cereals. The disease is transmitted by wheat curl mite rather than the corn leafhopper. However, laboratory testing is necessary to confirm the causal agent of the observed symptoms.

Herbicide Injury

The application of certain herbicides may cause symptoms that are mistaken for corn stunt. Stunted plants, plants with stacked nodes, or reddish discoloration of leaf tissue can all result from herbicide application errors or environmental conditions that increase crop sensitivity to herbicides (Figure 11).

How to distinguish herbicide injury from corn stunt: Symptoms typically occur shortly after herbicide application and often follow application patterns such as sprayer overlaps, skips, or drift. Damage is generally uniform within affected areas and does not spread over time. Reviewing herbicide application records and evaluating symptom distribution within the field can help distinguish herbicide injury from corn stunt.

Phosphorus Deficiency

Phosphorus deficiency in corn typically appears early in the season (vegetative growth stages) and can manifest as purpling and reddening of older leaves (Figure 12). Plants may be stunted with poor root development.

How to distinguish phosphorus deficiency from corn stunt: Soil and laboratory testing will be needed to distinguish phosphorus deficiency from corn stunt. Plants may “grow out” of phosphorus deficiency, and purpling color may lessen with age, but plants can still appear stunted. Laboratory testing can rule out the presence of the corn stunt pathogen in leaf tissue.

Late season purpling of corn plants

Several factors can cause corn to produce an excess of purple pigment called anthocyanin. Poor pollination, drought stress, ear removal, and animal feeding can all interfere with the flow of sugars produced by photosynthesis from the leaves and stalks to the ear. If the ear cannot use these sugars for grain filling, they accumulate in the leaf, sheath, and stalk tissue, resulting in purple discoloration.

How to distinguish purple corn syndrome from corn stunt: Since visual symptoms alone are not sufficient to diagnose corn stunt, laboratory testing is required to confirm the presence of the pathogens associated with the disease.

Disease Management

Management of corn stunt requires an integrated approach that combines cultural practices, host plant resistance, and management of the insect vector. Because there is no curative treatment for plants infected with corn stunt pathogens, management efforts should focus on suppressing corn leafhopper populations across the regional landscape, thereby preventing early infection of corn plants and reducing disease spread within and between fields. Key management strategies for corn stunt include:

Controlling volunteer corn

 Volunteer corn plants can serve as a “green bridge,” allowing both the corn leafhopper and corn stunt pathogens to survive between growing seasons in regions that do not experience a winter freeze sufficient to kill volunteer corn. Eliminating volunteer corn plants in fields helps eliminate the reservoir for corn stunt pathogens and the shelter for insect vectors during the off-season.

Planting strategies

One of the most important cultural practices to reduce the risk of corn stunt is planting corn as early as possible in the growing season. Early in the season, corn leafhopper populations are typically lower, reducing the risk of disease development. As the growing season progresses, corn leafhopper populations increase, and the proportion of insects carrying corn stunt pathogens also rises. As a result, late-planted corn is exposed to higher populations of infective corn leafhoppers carrying corn stunt pathogens during vulnerable growth stages and, consequently, has a greater risk of developing corn stunt and associated yield losses. Additionally, earlier-planted corn located near late-planted corn may experience increased movement of corn leafhoppers between fields, thereby creating conditions that favor corn stunt pathogen transmission.

Crop rotation

Crop rotation with non-grass crops such as soybean, cotton, peanut, and other broadleaf crops is recommended because the corn leafhopper reproduces only on Zea species. Although other grass crops such as wheat and sorghum are not suitable hosts for corn leafhopper reproduction, they may provide shelter and temporary food sources that help the insect survive during the off-season. For this reason, planting these grass crops in succession with corn is not recommended in areas previously affected by corn stunt. However, it is important to emphasize that the corn leafhopper has a high capacity for long-distance movement and can migrate between regions in search of newly planted corn fields. During these migrations, the insect may also spread corn stunt pathogens. As a result, crop rotation alone may be limited in its effectiveness as a management strategy for corn stunt.

Chemical control

Corn stunt has been suppressed through the application of insecticides targeting the insect vector, but curative tools and products targeting the corn stunt pathogens themselves are currently not available. For more information on insecticides available to manage corn leafhopper populations, contact your local Extension entomologist for recommendations and guidance tailored to local conditions and current pest pressure.

Plant tolerant corn hybrids when available

In countries where corn stunt has been a recurring problem, such as Brazil and Argentina, corn hybrids differ considerably in their susceptibility to the disease. However, information on the response of commercially available U.S. hybrids is currently unavailable.

Acknowledgements

The authors gratefully acknowledge funding for this project from the Southern IPM Center.

Authors

Maira R. Duffeck, Oklahoma State University; Ashleigh M. Faris, Oklahoma State University; Alison Robertson, Iowa State University; Anthony Zukoff, Kansas State University - Western KS Research and Extension; Damon L. Smith, University of Wisconsin-Madison; Darcy E. P. Telenko, Purdue University; Kiersten Wise, University of Kentucky; G. David Buntin, University of Georgia; Tom Allen, Mississippi State University; Travis Faske, University of Arkansas; Paul Esker, Penn State University; Ricardo A. Ramirez, New Mexico State University; Michael J. Brewer, Texas A&M AgriLife Research; José Santiago-González, Texas A&M AgriLife Extension; Dawson Kerns, Louisiana State University; Gary C. Bergstrom, Cornell University; Ivair Valmorbida, University of Missouri; Daisy Ahumada, North Carolina State University; Tom Isakeit, Texas A&M University; Rodrigo Onofre, Kansas State University; Tamra Jackson-Ziems, University of Nebraska-Lincoln; Heather Kelly, University of Tennessee; Pierce Paul, Ohio State University; Madalyn Shires, South Dakota State University; Ed Sikora, Auburn University; Nolan Anderson, Texas A&M University; Boris Camiletti, University of Illinois; Camilo Parada Rojas, Cornell University

Reviewers

Martin Chilvers, Michigan State University; Christian Krupke, Purdue University; Dean Malvick, University of Minnesota; Daren Mueller, Iowa State University; Boyd Padgett, LSU AgCenter; Nick Seiter, University of Illinois; Max Sturdivant, Clemson University; Albert Tenuta, Ontario Ministry of Agriculture, Food and Agribusiness

Sponsors

The authors gratefully acknowledge funding for this project from the Southern IPM Center (Grant S25-060) as part of USDA National Institute of Food and Agriculture Crop Protection and Pest Management Regional Coordination Program (Project Award No. 2022-70006-38002). Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. government determination or policy.

ChatGPT was used to generate Figure 9. All AI-generated content was carefully reviewed and verified by the authors. The authors take full responsibility for the content of this article.

How to cite: Duffeck, M. R., Faris, A. M., Robertson, A., Zukoff, A., Smith, D, L., Telenko, D. E. P., Wise, K., Buntin, G. D., Allen, T., Faske, T., Esker, P., Ramirez, R. A., Brewer, M. J., Santiago-Gonzalez, J., Kerns, D., Bergstrom, G. C., Valmorbida, I., Ahumada, D., Isakeit, T., Onofre, R., Jackson-Ziems, T., Kelly, H., Paul, P., Shires, M., Sikora, E., Anderson, N., Camiletti, B., Parada Rojas, C. 2026. An Overview of Corn Stunt. Crop Protection Network. CPN-2026. https://cropprotectionnetwork.org/publications/an-overview-of-corn-stunt.