Submitted to: Plant Protection Conference Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2003
Publication Date: 5/16/2004
Citation: Gottwald, T.R. 2004. The application of epidemiological analyses of citrus canker for the design of citrus canker eradication procedures in florida. 15th International Plant Protection Congress Proceedings. p. 477. Interpretive Summary:
Technical Abstract: Despite eradication efforts in both Florida and Brazil, citrus canker has been dispersed by a combination of storms and human movement. Citrus canker certainly causes crop losses put perhaps its most devastating effect is the social and political conflicts over mandated eradication programs. Epidemiological studies were conducted in both countries resulting in similar but unique approaches to disease management. In Florida, disease gradients were measured in urban Miami to determine if the practice of removing exposed trees within 125 feet (38 m) of diseased trees was adequate to curtail disease development. 18,000+ individual trees in dooryards were located via GPS, surveyed multiple times, and gradients measured for discrete 30-day intervals. Results suggested that the '125 ft-rule' was inadequate to suppress spread. Therefore, a panel of scientists and regulators examined the results and proposed that 1900ft (579 m) would better define diseased and exposed trees for removal. Subsequently in 2002, a 1900-ft eradication zone was signed into law by the Governor, challenged by numerous law suits, and eventually upheld by the Florida Supreme court. In Brazil studies were conducted to examine the change in the patterns of disease spread in commercial groves prior to and after the introduction of the Asian leafminer, whose feeding activities greatly exacerbate the disease. Disease gradients were found to be more extensive for post-leafminer epidemics. As a consequence, eradication regulations were changed by a new State law in São Paulo in 1999. Plantings with disease incidence > 0.5% are completely removed, whereas, for those with < 0.5% incidence, all trees within a radius of 30m of a diseased tree are destroyed. Additional studies in commercial citrus plantings in Brazil indicated that 98% of disease spread was contained within 2050 ft of previously infected trees.