Expert Working Group for a Pest Risk Analysis on Clavibacter nebraskensis, Goss’s bacterial wilt and leaf blight

Paris, 2025-12-01/04

Photo of the Expert Working Group

Clavibacter nebraskensis (Actinobacteria: Microbacteriaceae) was added to the EPPO Alert List considering its potential impact on maize in the EPPO region. In 2025, C. nebraskensis was selected as a priority for an EPPO PRA by the Working Party for Phytosanitary Regulations.

Clavibacter nebraskensis causes Goss’s wilt and leaf blight of maize, which, since its description in 1969, had been reported only in North America. In the mid-2000s-2010s, C. nebraskensis reemerged and the disease was observed in many maize-producing states in the USA causing losses. Currently, it is a managed pest of maize in the USA with impact mostly locally, on certain maize types or due to severe weather events. In 2024, Clavibacter nebraskensis was first found in South Africa in several provinces.

A Pest Risk Analysis (PRA) Expert Working Group (EWG) met at the EPPO headquarters in December 2025 to carry out this PRA for the EPPO region. The EWG assessed the potential pathways for the entry of C. nebraskensis into the EPPO region, potential for establishment and spread within the EPPO region, and evaluated impact in its area of current distribution and potential impact in the EPPO region.

The EWG finalised a draft PRA that describes the phytosanitary risk posed by C. nebraskensis to the EPPO region and associated uncertainties. The draft PRA will be reviewed by EPPO Core Members for PRA, the EPPO Panel on Phytosanitary Measures, and the Working Party on Phytosanitary Regulations. The PRA will then be made available at the EPPO Platform on PRAs.