Details on citrus tristeza closterovirus in Lebanon
In Lebanon, citrus is one of the main fruit crops and it is distributed throughout the country over an area of approximately 10,000 ha. Most citrus groves are located in the south, along the coast (Saida, Tyre), many others are in the north (mainly in the Akkar plains) and a few on Mount Lebanon. More than 95 % of citrus species are grafted onto sour orange (Citrus aurantium) rootstocks. Field surveys were carried out in autumn 1996 in commercial groves and nurseries to study the incidence of citrus tristeza closterovirus (EPPO A2 quarantine pest). The regions studied were the following: districts of Akkar and Tripoli in the North; districts of Awali, Wasta, Saida, Ghaziyyeh, Najjariyyeh, Aakaibeh, Gibehit, Addousiyyeh, and Maamoura in the South, and a small area on Mount Lebanon. A total of 3,427 trees (representative of the species and/or cultivars grown in Lebanon) were sampled and tested by ELISA. In addition, 1.110 citrus plants from 15 nurseries were also studied. 65 trees out of the 4.537 tested trees were found positive (62 trees from commercial groves in the north and in the south, 3 plants from a single nursery located in the north). However, none of the infected trees showed decline or clear symptoms of tristeza in the field. Results showed that the virus is more common than previously thought, as it was found in all studied regions (except Mount Lebanon). But the infection rate is low and most mother plants in nurseries are still free from the virus. Tests done on indicator plants showed that severe strains do not occur in Lebanon. The authors concluded that considering the wide distribution of citrus tristeza, the presence of vector (Aphis gossypii), and the fact that virtually the whole citrus industry is grafted onto sour orange rootstocks, eradication measures (destruction of infected trees) should be taken.
Sources
D'Onghia, A.M.; Saade, P.; Khoury, W.; Castellano, M.A.; Savino, V. (1998) Occurrence and distribution of citrus tristeza virus in Lebanon.
Phytopathologia mediterranea, 37(2), 75-78.