Outbreak of Xanthomonas axonopodis pv. citri in Florida
In USA, Xanthomonas axonopodis pv. citri (EPPO A1 quarantine pest) was introduced into Florida in 1912 and then into some other States. It was then eradicated from Florida in 1933 and from the other States by 1947. However, it was found again in Florida in 1986. An eradication programme was implemented and was thought to be successful until the 1995 record of the disease, which was found in private gardens in Miami but not in commercial citrus-growing areas (see EPPO RS 95/228).
An abstract of a paper to be presented at the next APS Annual meeting gives more details on the spread of X. axonopodis pv. citri in the urban area of Miami. In September 1995, citrus canker was found in private gardens in Dade County in Florida (US). Within 17 months, the infested area increased from 33 to 230 km2 despite all efforts. It is thought that inadvertent human transport has ensured short distance spread, whereas rainstorms and winds have contributed to long distance dissemination. Studies showed that a putative original focus of the disease was situated at 2.5 km south-east of the Miami International Airport. The oldest stem lesions in this focus area suggest the existence of citrus canker approximately 2-3 years before the first finding. It is also noted that the age of the newly infested areas is well correlated with individual tropical storms which have led to the spread of citrus canker 24 km to the north-east. It is concluded that the occurrence of storms combined with the damage of Phyllocnistis citrella resulted in a rapid increase of inoculum of X. axonopodis pv. citri.
Gottwald, T.; Graham, J.; Schubert, T.; Sun, X. (1997) Analysis of the dynamics of spread of citrus canker in urban Miami.
Abstract of a paper to be presented at the APS Annual Meeting, Rochester (US), 1997-08-09/13.
Phytopathology, 87 (6), Supplement, S34-S35.