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United States Department of Agriculture

Agricultural Research Service

Title: Florida actions toward HLB control

Authors
item Gottwald, Timothy
item Dixon, T. R. - FDACS

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: July 14, 2006
Publication Date: July 22, 2006
Citation: Gottwald, T.R., Dixon, T. 2006. Florida actions toward HLB control. Proceedings of the International Workshop on Citrus Greening, July 14-21, Ribeiro Preto, Brazil. p.67-68.

Technical Abstract: The Florida citrus industry has suffered major disease setbacks in 2005-2006. The fall 2005 discovery of huanglongbing (HLB) in Florida was just a few months before the decision to halt the citrus canker eradication program because of the predicted massive spread of citrus canker over much of southern Florida by hurricane Wilma. In late 2005, USDA/APHIS and the FDACS/DPI convened a science panel of US HLB experts to assess the distribution of the disease and recommend a course of action. After examining preliminary survey results and reviewing prior knowledge of HLB, its biology and vector transmission, the science panel opined that the disease was already too widespread to attempt eradication and had become endemic to Florida. Ultimately, management strategies for HLB and citrus canker must be developed to reflect the similarities as well as the differences between the two diseases. Although the two diseases differ significantly in etiology and epidemiologically, they are both considered exotic diseases and are therefore subjected to regulatory control at some level but no longer considered candidates for eradication. No complete and systematic delimiting survey for HLB has been undertaken. However, subsequent surveys have shown that the disease has already spread to 12 counties across southern Florida. Therefore, the science panel recommended a detailed survey should be conducted to both delimit the HLB infection and determine the severity of HLB within infected areas. In addition, concern for the spread of citrus canker within the state and regulatory impediments to interstate shipment of citrus fruit due to an endemic prevalence of citrus canker have necessitated continued survey for canker as well. Thus, a combined HLB/Citrus Canker statewide commercial planting survey has been designed and will be implemented in summer 2006. To accomplish this all citrus plantings within the state of Florida are ranked by susceptibility to both HLB and citrus canker relative to their respective citrus species/cultivar type and regulatory manpower and fiscal resources were assessed to determine how much area can be surveyed within a 90-day timeframe. A software routine was developed to stochastically select approximately 15% of the commercial citrus area that resides within each section (259 ha = 1 mi2) for the combined survey. A this point, the survey is slightly biased toward HLB, but also provides adequate emphasis on commercial plantings susceptible to citrus canker as well. This sampling protocol can also be used in other citrus-producing states such as Texas, California, and Arizona and serve as an early detection survey for these two diseases. The science panel also recommended a review of possible disease mitigation/control options including roguing, biocontrol, and insect vector control and immediate nursery certification program changes. The University of Florida has taken the lead in developing best management practices relative to both HLB and citrus canker. In addition, the USDA/APHIS, FDACS/DPI and commercial citrus industries have undertaken the development of a Citrus Health Response Plan (CHRP) to develop minimum standards and national guidelines and protocols for citrus budwood protection, commercial citrus nurseries, producers, harvesters, packinghouses, and residential citrus to best contain HLB as well as citrus canker, and mitigate spread of both diseases. Overarching issues for both diseases are exclusion and sanitation protocols. Control/mitigation of HLB is predicated on prior experience with this disease in Southeast Asia and South Africa. A multiyear, multi-country UNDP-FAO collaborative project in Southeast Asia focused recommendations on nursery certification, removal of infected trees and vector control. However, these recommendations have been founded predominately on anecdotal observations, and non-replicated scientific studies. Therefore, USDA/ARS and the University of Florida are collaboratively testing these disease mitigation/control options in replicated studies in commercial plantings in Florida to assess the relative effect of each practice and develop maximized HLB management strategies for Florida. Similar testing is being conducted in Brazil.

Last Modified: 10/31/2014
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