Candidatus Liberibacter sp. - undescribed species
Significance: As a precautionary measure, Ministry of Agriculture and Forestry (MAF) Biosecurity New Zealand recently suspended exports of tomatoes and peppers. This action follows the January (2008) discovery of an apparently new disease-causing bacterium in three commercial greenhouses in the Auckland area of the North Island. MAF Biosecurity New Zealand reported the bacterium as a previously undescribed species of Candidatus Liberibacter. Tests indicate the bacterium does not match any of the currently known species in the Candidatus Liberibacter genus. Initial findings suggest it may be transmitted by the tomato/potato psyllid (Bactericera cockerelli), an insect that was recently introduced and now established in New Zealand. Disease symptoms in both tomatoes and peppers vary across varieties and growing conditions. In tomatoes, symptoms include leaf curling and yellowing, stunting of plants, and uneven or distorted fruit development. In peppers, symptoms include pale green or yellow distorted leaves with shortened stalks, flower drop, and dieback of plant parts. Further research is still needed on the epidemiology of the bacterium, what the full impact might be on tomato, pepper, or other hosts, and how to manage the pathogen.
Issues of Concern: Only a few members of Candidatus Liberibacter, a genus of fastidious phloem-inhabiting bacteria, have ever been characterized. The genus includes the pathogen that causes citrus greening or huanglongbing (HLB), a very damaging Citrus pathogen that is transmitted by the citrus psyllid. The suspected vector of this new Liberibacter species, Bactericera cockerelli, has a wide host range that includes species in 20 plant families, however a strong preference for Solanaceous species is noted. Besides its vectoring abilities, the feeding damage of this psyllid on its hosts is considered a problem in some parts of the world. In some potato and tomato production areas of North America feeding by the nymph stage can lead to a disease called "psyllid yellows". Until more is known about this disease, it is difficult to assess its potential importance.
MAF Biosecurity New Zealand. 2008. New bacterium affects fresh tomatoes and capsicums. http://www.biosecurity.govt.nz/pests/surv-mgmt/resp/tom-cap-bacterium. MAF Biosecurity New Zealand. No Date. Pest Datasheet for Potato/Tomato Psyllid: Bactericera cockerelli. http://www.biosecurity.govt.nz/pests-diseases/plants/potato-tomato-psyllid.htm. ProMED Plant, 4 June, 2008. Liberibacter Species, Tomato and Capsicum - New Zealand: New Pathogen. A ProMED-mail post. sourced from NZ Ministry of Agriculture and Forestry (MAF) media centre [edited] http://www.maf.govt.nz/mafnet/press/2008/080604tomatoes.htm. Trumble, J. 2008. The Tomato Psyllid: A New Problem on Fresh Market Tomatoes in California and Baja Mexico. Ventura County Cooperative Extension. Department of Entomology, University of California, Riverside. http://ceventura.ucdavis.edu/Vegetable_Crops/Tomato_Psyllid.htm. UCDavis. 2008. UC Pest Management Guidelines: Tomato Psyllid. University of California, David. http://www.ipm.ucdavis.edu./PMG/r783303011.html. UCDavis. 2008. UC Pest Management Guidelines: Potato Psyllid. University of California, Davis. http://www.ipm/ucdavis.edu/PMG/r607300811.html.