Monitoring of Citrus Tristeza Virus and its vectors on citrus nurseries in eastern Sicily
Abstract: Citrus Tristeza Closterovirus (CTV) is considered one of the most destructivediseases for citrus in the world. In Italy it was first detected in the ‘50s and monitored in the‘80s in a restricted area. Recently the virus spread widely in the citrus area of Southern Italy,where trees are grown almost exclusively on sour orange, a very susceptible rootstock. In1996, a regulatory act, the “Decreto Ministeriale 22/11/1996”, was issued for the eradicationof the virus promoting the monitoring of the citrus cultivated area. In the period 2006-09, inthe framework of the official controls, a monitoring activity was carried out in Eastern Sicilyfor the detection of CTV on citrus trees cultivated in nursery conditions. The diffusion ofaphids was also surveyed in order to exclude the presence of Toxoptera citricidus, recentlydetected in the North-Western area of the Iberian Peninsula. This aphid is known as a veryefficient vector of CTV. In the survey period a total of 1,544,359 nursery trees was checkedutilizing DAS-ELISA test, and 117,000 nursery trees were observed for the identification ofaphids species present on new shoots. The incidence of infected trees ranged from 3.5% in2006 to 0.25% in 2007 and 2009. All infected plots were destructed. A protected foundationblock for budwood production, containing 45 accessions, was monitored starting from 2007,sampling a total of 1042 mature trees. In 2009, CTV was detected in the foundation block.The quarantine aphid T. citricidus was not observed in the survey period. In spring and fallsamples, the presence of Aphis gossypii, A. spiraecola and T. aurantii, very common in theMediterranean area, was recorded in decreasing order.