Details on the situation of Citrus tristeza closterovirus and its vector Toxoptera citricida in Belize
Citrus tristeza closterovirus (CTV - EPPO A2 list) was discovered in Belize in 1984, on 74 sites in the Stann Creek Valley. Several surveys have been carried out since then. In 1993, a survey showed that 14.9% of samples were positive for CTV mild strains and 4 % for the severe strains. Since the discovery of CTV, growers have been advised to use CTV-tolerant rootstocks. In 1994, a certification programme was initiated. In 1996, the presence of Toxoptera citricida (Homoptera: Aphididae - EPPO A1 list), which is an efficient vector, was noticed on Belize. This introduction initiated further studies on the situation of CTV, in particular in orchards of citrus grafted on sour orange rootstocks (Citrus aurantium). Four plots of Valencia orange grafted on sour orange rootstocks were selected on the basis for their high and low CTV infection levels. Observations and tests were done during a six-year period (1997 to 2003). Results showed fluctuations in infection levels but no decline symptoms were observed in the tested plots. It is noted that the impact of CTV spread by T. citricida has varied among Caribbean countries. In Jamaica, a widespread decline of trees grafted on sour orange was observed soon after the introduction of the aphid. In Dominican Republic, only mild strains were detected after the introduction of T. citricida. However, in 1996 severe strains started to be detected and decline symptoms were observed in 1998, which may indicate that the severe strains were introduced after the vector.
Sources
Manzanero Majil, V. (2004) Citrus tristeza virus (CTV): its development in Belize.
Caraphin News, no. 24, June 2004, 1-4.