Surveys on huanglongbing in Spain: absence of the disease and more details about Trioza erytreae
In the EPPO region, huanglongbing (associated with ‘Candidatus Liberibacter asiaticum’, ‘Ca. L. africanus’, ‘Ca. L. americanum’ – EPPO A1 List) is still absent but the detection of one of its vectors, Trioza erytreae (Hemiptera: Triozidae – EPPO A2 List), in the Iberian Peninsula has triggered intensive surveys in Spain and the development of a contingency plan. It is recalled that T. erytreae was first detected in Madeira (Portugal) in 1994, in Islas Canarias (Spain) in 2002 and then in the mainland along the Atlantic coast in Portugal and Spain (Galicia). Extensive surveys were conducted in Islas Canarias and Galicia from 2009 to 2015 and confirmed the absence of huanglongbing.
Islas Canarias
Survey results showed that T. erytreae occurs in El Hierro, Gran Canaria, La Gomera, La Palma, Tenerife, but is still absent from Fuerteventura, La Gracioza, and Lanzarote. On islands where the pest occurs, almost all monitored commercial citrus crops were infested. In general, the most affected citrus species were lemon (Citrus limon) and mandarin (C. reticulata) trees, whereas sweet and sour orange (C. sinensis and C. aurantium) trees were less damaged by the insect. From a total of 108 270 inspected trees in Islas Canarias, 3 355 were tested for the presence of ‘Ca. Liberibacter’ species, as well as 1 464 specimens of T. erytreae. None of the ‘Ca. Liberibacter’ species associated with huanglongbing were detected.
Galicia
The monitored areas covered the provinces of Pontevedra and A Coruña. Results showed that T. erytreae occurs in the western part of both provinces, near the border with Portugal and along the Atlantic coast. A total of 2 735 trees were studied and 66% of the inspected trees showed signs of the presence of T. erytreae, in many cases only mature leaves of a few shoots were showing leaf galls. Although lemon trees were the most severely affected, damage could also be observed in mandarin, sweet and sour orange, as well as in grapefruit (C. paradisi) trees. From a total of 2 735 inspected trees, 1 941 were tested, as well as 105 specimens of T. erytreae. As for Islas Canarias, none of the ‘Ca. Liberibacter’ species associated with huanglongbing were detected.
Sources
Siverio F, Marco-Noales E, Bertolini E, Teresani GR, Peñalver J, Mansilla P, Aguín O, Pérez-Otero R, Abelleira A, Guerra-García A, Hernández E, Cambra M, López MM (2017) Survey of huanglongbing associated with ‘Candidatus Liberibacter’ species in Spain: analyses of citrus plants and Trioza erytreae. Phytopathologia Mediterranea 56(1), 98-110.