EPPO Alert List – Clavibacter nebraskensis

Damage done by Clavibacter nebraskensis on Canadian corn. 

Image credit Harding et al. 2018

Why: Clavibacter nebraskensis causes Goss’s wilt and leaf blight of maize in North America. In recent years, its occurrence and impact has increased in the USA, and it was recently reported from Mexico and South Africa. Considering its potential impact on maize in the EPPO region, the EPPO Secretariat considered it useful to add it to the EPPO Alert List. 

Where: C. nebraskensis was first described in the USA, but recent research suggests that it may originate from Mexico.

Africa: South Africa.

North America: Canada (Alberta, Manitoba), Mexico, United States of America (Colorado, Illinois, Indiana, Iowa, Kansas, Louisiana, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota, Texas, Wisconsin, Wyoming).

On which plants: Maize (Zea mays) is the only economic host. A number of Poaceae species are reported to act as secondary hosts for C. nebraskensis.

Damage: C. nebraskensis is a Gram-positive, non-flagellated, non-spore forming, aerobic coryneform bacterium that forms yellow colonies on most growth media. It causes large (2–15 cm) tan to grey elongated oval lesions with wavy, irregular water-soaked margins on maize leaves. The lesions often start at the leaf tip or are associated with wounding caused by hail or wind damage. Early infection may become systemic and cause seedlings to wilt, wither, and die. Significant yield losses of up to 50% have been recorded. 

Goss's wilt symptoms, development, and effect on yield are similar to those caused by Pantoea stewartii subsp. stewartii (EPPO A2 List). In fact, C. nebraskensis was once considered a more virulent and orange-coloured strain of P. stewartii subsp. stewartii.

Goss’s wilt and leaf blight became a major maize disease in the 1970s in the USA before nearly disappearing in the mid-1980s. It unexpectedly re-emerged in 2004 in Colorado and Nebraska, spreading across the central High Plains and expanding to other Midwest states, including Indiana. The re-emergence of the disease is thought to be favoured by new cultural practices such as continuous cropping, reduced tillage, and overhead sprinkler irrigation, as well as climate change. There is no chemical treatment available to control Goss's wilt in the field. C. nebraskensis-resistant hybrids have been recently developed. 

Dissemination: Seed transmission occurs in maize, although at very low rates. In the areas where the pest is present, the main source of inoculum is infected plant debris. 

Pathways: seed of Zea mays from countries where the pest occurs. 

Possible risks: Maize is an economically important crop which is cultivated across the EPPO region. The disease occurs in areas with climates similar to the ones in the EPPO region and is likely to cause similar impacts. 

Sources 

CABI (2020) Datasheet on Clavibacter nebraskensis (Goss's bacterial wilt and leaf blight). https://doi.org/10.1079/cabicompendium.15339

Flores-López LF, Olalde-Portugal V, Vidaver AK, Morales-Galván Ó, Hernández-Rosales M, Huerta AI (2024) Unlocking a mystery: characterizing the first appearance of Clavibacter nebraskensis in Mexican cornfields. Plant Disease 108(5), 1374-1381. https://doi.org/10.1080/07060661.2018.1506502 

Harding MW, Jindal K, Tambong JT, Daayf F, Howard RJ, Derksen H, Reid LM, Tenuta AU, Feng J (2018) Goss’s bacterial wilt and leaf blight of corn in Canada–disease update. Canadian Journal of Plant Pathology 40(4), 471-480.

IPPC website. Official Pest Reports- South Africa (2025-01-14): Notification on the detection of Clavibacter michiganensis subsp. nebraskensis, Goss’ Wilt on maize, in the Republic of South Africa  https://www.ippc.int/fr/countries/south-africa/pestreports/2025/01/notification-on-the-detection-of-clavibacter-michiganensis-subsp-nebraskensis-goss-wilt-on-maize-in-the-republic-of-south-africa/

Langemeier CB, Robertson AE, Wang D, Jackson-Ziems TA, Kruger GR (2017) Factors affecting the development and severity of Goss's bacterial wilt and leaf blight of corn, caused by Clavibacter michiganensis subsp. nebraskensis. Plant Disease 101(1), 54-61.

Li X, Tambong J, Yuan K, Chen W, Xu H, Lévesque CA & De Boer SH (2018) Re-classification of Clavibacter michiganensis subspecies on the basis of whole-genome and multi-locus sequence analyses. International Journal of Systematic and Evolutionary Microbiology 68, 234-240.

Osdaghi E, Robertson AE, Jackson‐Ziems TA, Abachi H, Li X, Harveson RM (2023) Clavibacter nebraskensis causing Goss's wilt of maize: Five decades of detaining the enemy in the New World. Molecular Plant Pathology 24(7), 675-692. https://doi.org/10.1111/mpp.13268

EPPO RS 2025/057 

Entry date 2025-02