Using models to provide rapid programme support for California's efforts to suppress Huanglongbing disease of citrus

Authors: MCROBERTS, NEIL - University Of California; GARCIA FIGUERA, SARA - University Of California; OLKOWSKI, SANDRA - University Of California; MCGUIRE, BRIANNA - University Of California; LUO, WEIQI - North Carolina State University; POSNY, DREW - North Carolina State University; Gottwald, Timothy

Submitted to: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2019
Publication Date: 5/20/2019
Citation: McRoberts, N., Garcia Figuera, S., Olkowski, S., McGuire, B., Luo, W., Posny, D., Gottwald, T.R. 2019. Using models to provide rapid programme support for California's efforts to suppress Huanglongbing disease of citrus. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 374(1776). https://doi.org/10.1098/rstb.2018.0281.
DOI: https://doi.org/10.1098/rstb.2018.0281

Interpretive Summary: An epidemiological research team including scientists from UC Davis, USDA, ARS and. North Carolina State Univ. was formed to address issues and questions posed by the Calif. Dept. of Food and Agriculture (CDFA) relating to the introduction, spread, and control/mitigation of the invasive citrus disease, Huanglongbing (HLB) into California. The epidemiology team analyses disease and vector data in California relative to HLB and provides the analyses and interpretations to an elected committee of growers and industry leaders. This committee in collaboration with CDFA has the regulatory authority to enforce disease control measures including removal of HLB-infected trees. This paper describes how the epidemiology team have devised survey methods for the disease and vector and have provided suggestions on resource allocation between survey for disease detection versus survey for delimitation of the diseased area. In addition we describe how the team’s analyses have been used to support rule-making to enact costly but beneficial regulations. The impact of this endeavor is to provide timely epidemiologically sound deliverables to the CDFA for decision making which indirectly supports the California Citrus industry in it’s battle against HLB.

Technical Abstract: We describe a series of operational questions posed during the state-wide response in California to the arrival of the invasive citrus disease Huanglongbing. The response is coordinated by an elected committee from the citrus industry and operates in collaboration with the California Department of Food and Agriculture, which gives it regulatory authority to enforce the removal of infected trees. The paper reviews how surveillance for disease and resource allocation between detection and delimitation have been addressed, based on epidemiological principles. In addition, we describe how epidemiological analyses have been used to support rule-making to enact costly but beneficial regulations and we highlight two recurring themes in the programme support work: (i) data are often insufficient for quantitative analyses of questions and (ii) modellers and decision-makers alike may be forced to accept the need to make decisions on the basis of simple or incomplete analyses that are subject to considerable uncertainty.