Scientific Opinion on the pest categorisation of Clavibacter michiganensis subsp. michiganensis (Smith) Davis et al.

The European Commission requested the EFSA Panel on Plant Health to perform the pest categorisation for Clavibacter michiganensis subsp. michiganensis (Cmm). The agent responsible for vascular tomato wilt and canker is the clearly defined and valid gram-positive taxon C. michiganensis subsp. michiganensis. This pathogen can be accurately identified based on a range of sensitive and specific methods. Tomato (Solanum lycopersicum) is the main host, but peppers (Capsicum annum and C. frutescens) are also naturally susceptible to Cmm. These host plants are cultivated throughout Europe and conditions are conducive to disease development in open fields in southern Europe and in greenhouses. The disease is present in many EU Member States. Outbreaks are rare but usually severe. It causes a range of symptoms on the aerial parts of plants, including the fruits. Detection methods are available for any type of plant material either presenting symptoms or symptomless. Seed testing has proven to be a good control option by discarding contaminated seed lots. Despite tomato seed production being done under strict sanitation using recommended practices, seed contamination still occurs occasionally. Contaminated seeds and transplants are responsible for long-distance dissemination of the pathogen. Under conducive conditions, even low levels of seed contamination can result in disease outbreaks. Cultivation practices can favour secondary spread of the bacterium and an increase in disease incidence both in greenhouse and in open-field crops. No effective biological or chemical control agents are registered for bacterial canker in Europe. Cmm meets all criteria defined in International Standard for Phytosanitary Measures (ISPM) 21. Cmm meets all ISPM 11 criteria, although it has been observed in 16 EU Member States. The outbreaks are usually severe but sporadic.