Bayesian Analysis for Inference of an Emerging Epidemic: Citrus Canker in Urban Landscapes

Neri, Franco M.; Cook, Alex R.; Gibson, Gavin J.; Gottwald, Tim R.; Gilligan, Christopher A.

Asiatic citrus canker (ACC) is caused by the bacterium Xanthomonas axonopodis pv. citri (Xac). The pathogen can infect a very wide range of citrus and related hosts, causing defoliation, fruit blemishing and severe losses in quality and quantity of yield [29] . The pathogen is principally spread by wind-blown rain [29, 30] . It is not vector borne, other than by anthropomorphic transmission on machinery [29] , but the spread is known to be exacerbated by leaf damage inflicted by the Asian leaf miner Phyllocnistis citrella that first appeared in Florida in 1993. There have been several independent introductions of Xac into Florida up until the mid 1990s [31] . The pathogen was originally introduced on imported seedlings from Japan in 1910 and declared eradicated, after extensive removal of infected and exposed susceptible trees, in 1933. An outbreak in Manatee county on the west coast of Florida was thought to have been eradicated in the 1980s, but ACC reoccurred within two years from surviving inoculum. A new infestation of ACC from a genetically different strain of Xac was reported in urban Miami on residential trees in 1995. The disease spread rapidly through Eastern and central Florida [29] , triggering an extensive eradication programme, involving compulsory removal of ,7M commercial, .4M nursery and 0.8M residential trees around infected sites, at a cost of .$1 billion. The eradication scheme was halted in 2006 following widespread dispersal of inoculum during several severe hurricanes in 2004 and the eventual determination that the disease had become endemic rendering eradication unattainable [32] .