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United States Department of Agriculture

Agricultural Research Service


item Gottwald, Timothy

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/30/2005
Publication Date: 11/7/2005
Citation: Gottwald, T.R. 2005. Citrus canker: doing battle with the beast for nearly a century. Second International Citrus Canker and Huanglongbing Workshop, Orlando, FL, November 7-11, 2005. C1,p.11.

Interpretive Summary:

Technical Abstract: Asiatic citrus canker (ACC) has a long history in Florida. The disease was first found around 1910 and spread throughout the southeastern US on imported citrus seedlings from Japan. After an extensive eradication program, canker was declared eradicated from Florida and the adjacent states in 1933. Citrus canker was discovered again in Manatee Co. Florida south of Tampa Bay in 1986, and was declared eradicated by 1994. Three years later the disease re-emerged on the west coast of Florida where the 1980s outbreak had occurred. Concurrently, a new epidemic of ACC was discovered in urban Miami in 1995, with an estimated introduction some time in 1992 or 1993. When first detected in Miami in 1995, the epidemic area was approximately 36.3 km2 (14 mi2) of largely residential properties southwest of the Miami International Airport. Over the past decade ACC has spread throughout most production areas of Florida. In response to the 1995 detection of citrus canker, a cooperative state/federal citrus canker eradication program (CCEP) was established between the Florida Department of Agriculture and Consumer Services (FDACS), Division of Plant Industry (DPI) and the USDA, Animal and Plant Health Inspection Service (APHIS). The introduction of the Asian leafminer which exacerbates ACC outbreaks, combined with numerous hurricanes, tropical storms, severe local weather, mechanical-human movement of plant material, legal challenges curtailing eradication for multiple years, and inattentiveness by some to sanitation protocols, has lead to the critical situation currently facing the Florida citrus industry. As eradication has progressed, various unique isolates of the causal bacteria, Xanthomonas axonopodis pv citri (Xac) have been discovered and characterized. The presence of multiple isolates is indicative of multiple introductions of Xac and demonstrates the porosity of international borders even when subject to vigilant surveillance and regulatory controls to prevent importation of exotic pests and pathogens and further demonstrates the necessity for perpetual post-introduction surveillance systems, such as the residential sentinel survey and the multiple commercial survey methods presently deployed. A challenge for any eradication program is to develop criteria that accurately evaluate the effectiveness of eradication. One critical criterion is the continual reevaluation of the incidence and distribution of the disease. For the ACC eradication campaign in Florida, manpower and resources became limiting in 2005 following the 2004 hurricane season which resulted in numerous outbreaks of canker in previously disease-free areas of the commercial citrus industry. New survey strategies were developed including the targeted grove survey (meteorological event driven), sentinel grove survey, and the commercial producer self survey. These were combined with existing grove, residential sentinel, and delimiting surveys to rapidly and systematic blanket the commercial industry to find and delimit post-hurricane infections. Another and perhaps more important criterion to evaluate, is the threshold of disease beyond which eradication is no longer biologically possible. However, there are other thresholds that may be even more critical from a commercial industry perspective, such as economic, political and social thresholds for disease tolerance. The relative importance of the socio-economic/political thresholds and their relationship to one another and to the biological threshold can change depending upon the criteria used to evaluate them. These and other eradication issues will be discussed.

Last Modified: 06/25/2017
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