‘Candidatus Liberibacter asiaticus’ does not occur in Portugal
In summer 2015, the presence of ‘Candidatus Liberibacter asiaticus’ (EPPO A1 List) was suspected in one orchard located in Silves county (Algarve region), Portugal. The grower reported symptoms of leaf yellowing on 20 year-old citrus trees (Citrus sinensis). These symptoms appeared in spring/summer 2014, disappeared during winter but reappeared in spring 2015. The Regional and Central Plant Protection Services inspected the orchard on 2015-08-24 and noted the presence of symptoms on approximately 80% of the trees. Six samples were taken from 6 symptomatic trees and sent to the Portuguese Official laboratory (INIAV) for testing ‘Candidatus Liberibacter spp.’ and Xylella fastidiosa. On 2015-10-23, the laboratory reported that 1 of the 6 samples tested positive for ‘Ca. L. asiaticus’ (all results were negative for X. fastidiosa).
Immediately after receiving the laboratory (INIAV) report which indicated a suspicion of ‘Ca. L. asiaticus’ in 1 sample, 12 samples were taken from the same trees. Half of these samples were sent to the French reference laboratory (ANSES) for testing for ‘Ca. Liberibacter spp.’ and the other half was sent to INIAV for testing for ‘Ca. Liberibacter spp.’ and Xylella fastidiosa. All tested samples gave negative results. In addition, 8 samples composed of fresh leaves and DNA extracts were also sent to ANSES. Similarly, all results were negative for ‘Ca. Liberibacter spp.’. As a precaution, official phytosanitary measures were taken in the orchard from which the initial suspect sample had been taken. In December 2015, all plants and fruit were burnt in situ. An intensive monitoring and sampling programme was initiated in the surrounding area in 2 other plots belonging to same grower and in nearby 3 nurseries. In total 61 plots were inspected and 100 samples from host plants were collected and sent to INIAV for testing. The analysis of these 100 samples has now been completed and all results were negative for ‘Ca. Liberibacter spp’. Finally, intensive inspections for insect vectors were carried out at the same sites and no evidence of their presence was found. Until now, 142 traps have been installed in the orchards located in the surroundings and in nurseries. These traps were inspected once every two weeks, and sent to INIAV for examination. The results were consistent with the outcome of the specific surveys that had been carried out for the known vectors of ‘Ca. Liberibacter asiaticus’ in recent years. The only insects identified in the orchard and surrounding areas were whiteflies (Aleurothrixus floccosus), aphids (Aphis spiraecola and A. gossypii), mites, scale insects and the cicadellid Penthimiola bella. Diaphorina citri has never been detected in Portugal, and Trioza erytreae has been found only in the northern part of the country. Monitoring and sampling of host plants will resume in spring 2016.
The pest status of ‘Candidatus Liberibacter asiaticus’ in Portugal is officially declared as: Absent.
Sources
NPPO of Portugal (2016-02).