PREVALENCE OF SEVERE STRAINS OF CITRUS TRISTEZA VIRUS IN FLORIDA CITRUS NURSERIES

Sixty-eight percent of the 'Pineapple', 52 % of the 'Navel', 46 % of t he 'Valencia', 38 % of the 'Hamlin', and 0 % of the 'Ambersweet' orang e [Citrus sinensis (L.) Osh.] trees in five Florida citrus nurseries w ere infected with severe strains of citrus tristeza virus (CTV), as de monstrated by reaction with a monoclonal antibody specific for severe strains of the virus. Severe strains of CTV infected 4 %, 46 %, 76 %, 30 %, and 48 % of the trees at each of the five nurseries, respectivel y, indicating a considerable difference in severe strain prevalence am ong the nurseries. Thirty-five percent of the trees in the scion block s (budwood source) of the nurseries also contained severe strains of C TV.