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United States Department of Agriculture

Agricultural Research Service


Location: Subtropical Plant Pathology Research

Title: Risk-based residential HLB/ACP survey for California, Texas and Arizona

item Gottwald, Timothy
item Luo, Weiqi
item Mcroberts, N

Submitted to: Plant Management Network
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2013
Publication Date: 10/1/2013
Publication URL:
Citation: Gottwald, T.R., Luo, W., Mcroberts, N. 2013. Risk-based residential HLB/ACP survey for California, Texas and Arizona. Plant Management Network. Webcast.

Interpretive Summary: This webcast will help consultants, growers, regulators and other practitioners in the Florida, Texas, California and Arizona citrus growing regions to understand and employ a risk based urban survey for early detection of Citrus Huanglongbing (HLB). HLB is a devastating citrus disease threatening many citrus industries and growing regions worldwide. The capacity for HLB to increase very rapidly highlights the importance of early detection and response when dealing with exotic and invasive diseases; developing a detection protocol for HLB for California, Texas and Arizona is the primary objective of this research. The importance of an effective detection system for HLB is underlined by the existence of the large urban citrus population with no disease or vector control that exists as a mixed landscape with commercial citrus production and which poses a continual treat of vector and disease immigration. By the end of the presentation, concerned stakeholders will understand the underlying survey model and risk factors utilized to develop an overall risk algorithm that is used to maximize targeting of manpower and resources and optimize disease/vector detection and response.

Technical Abstract: The recent discoveries of HLB in the Los Angeles Basin and the Rio Grande Valley of Texas underscore the imminent danger of HLB spread in these two States and the urgent need for highly sensitive survey methods for early detection of new residential infections of HLB combined with rapid intervention to contain and eliminate further spread. Sampling efforts need to be deployed based on potential risk introduction and threat to commercial citrus to optimize early detection. A risk-based residential survey has recently been constructed and deployed in Southern California and the Rio Grande Valley of Texas, and Arizona. An overall risk algorithm is constructed considering several major components of risk: 1) residential citrus populations, 2) potential spread of the psyllid vector, 3) Vector population prevalence and dynamics, 4) citrus fruit transportation corridors, 5) climatological effects, 6) population demographics, 7) border crossings into the US from Mexico where the disease is prevalent, and 8) risk of HLB positive find and bacteria positive vectors. Sampling intensity is adjusted via proximity to commercial citrus. Deployment to regulatory and industry stakeholders includes: 1) Overall mapping of cumulative total risk calculated for each of the regions of concern for each state, 2) Survey protocol in the form of risk maps provided to each state/agency, and 3) An output data set in Excel that lists each square-mile are and its estimated total risk. The survey models also provide a modeling framework for development of surveys for other citrus producing areas and industries such as areas in Central and South America and the Caribbean. A similar framework can be easily transferred to apply to survey other non-indigenous diseases when required. In the global sense, surveys that can predict and detect introductions before or while in low incidence will afford improved chances of disease suppression/management prior to areawide or regional spread that can eventually act as sources for future introductions into the US.

Last Modified: 10/18/2017
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