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United States Department of Agriculture

Agricultural Research Service

Title: Post-Hurricane Analysis of Citrus Canker Ii: Predictive Model Estimation of Disease Spread and Area Potentially Impacted by Various Eradication Protocols Following Catastrophic Weather Events

item Gottwald, Timothy
item Irey, Michael

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 23, 2007
Publication Date: May 23, 2007
Citation: Gottwald, T.R., Irey, M.S. 2007. Post-hurricane analysis of citrus canker ii: predictive model estimation of disease spread and area potentially impacted by various eradication protocols following catastrophic weather events. Plant Health Progress. doi:10.1094/PHP-2007-0405-01-RS.

Interpretive Summary: This second paper in a series extends the citrus canker hurricane spread model presented in the first paper in the series. In this paper, the model is adjusted for distance of spread and the model is applied across the state of Florida. Estimations for the model are presented that use known points of infection of citrus canker that existed in the state at the time hurricane Wilma passed through the state in October 2005. The model estimates those acres of commercial citrus that will potentially be affected by citrus canker infections due to the hurricane spread of the bacteria and subsequent local spread over the 14-month period following hurricane Wilma. These estimations have been used by the state and federal regulatory agencies to determine that citrus canker is now endemic in the state of Florida, cannot be eradicated feasibly, and therefore justifies the end of the citrus canker eradication program.

Technical Abstract: The affect of 2005 Hurricane Wilma on the dissemination of Xanthomonas axonopodis pv. citri (Xac), the cause of Asiatic citrus canker (ACC), and subsequent disease development was examined and predictions for the areas into which Xac was likely to have spread from known sources of infection was developed. In addition, the effect of the current 1900-ft (579-m) ACC eradication protocol, resulting in removal of all ‘exposed trees’ with a 1900-ft radius of a known Xac-infected tree, was calculated via GIS analysis and expressed as the predicted ‘impacted area’. The GIS calculations were based on the extension of the previous published wind-rain index vector (WRIV) model. The model extension consisted of the incorporation of an estimate of distance of spread due to hurricanes from data collected during the 2004 hurricane season. An inverse power law dissemination function was used to describe regional dispersal from a point focus of Xac-infection. Alternative eradication protocol (distances) to the 1900-ft protocol were evaluated in association with the GIS analyses and used to examine the effect of eradication distance on predicted ‘impacted area’. The results of these analyses were used by state and federal regulatory agencies and commercial citrus producer groups to evaluate the feasibility of continued ACC eradication.

Last Modified: 4/22/2015
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