Huanglongbing disease putting the squeeze on OJ production in Florida

Authors: Stover, Eddie

Submitted to: American Society of Horticulture Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/16/2020
Publication Date: 8/5/2020
Citation: Stover, E.W. 2020. Huanglongbing disease putting the squeeze on OJ production in Florida. American Society of Horticulture Science Meeting. P.34072. https://ashs.confex.com/ashs/2020/meetingapp.cgi/Paper/34072.
DOI: https://doi.org/10.ashs.2020.Paper.34072

Interpretive Summary:

Technical Abstract: Huanglongbing (HLB) citrus disease was first unequivocally described from China in the 1940s. It is caused by a bacterium (Candidatus Liberibacter asiaticus, CLas) which is limited to the phloem in citrus, is vectored by the Asian citrus psyllid (Diaphorina citri), has a long latency period, and is graft-transmissible. CLas has a greatly reduced genome, and as an obligatory endophyte relies on its host for many of its needs. The citrus pathology community in the US was keenly aware of the threat of HLB prior to its arrival in the United States, participated in many international conferences and some HLB research, and kept United States industries apprised of this potent threat. The insect vector quickly became widespread in Florida following its first identification in 1998, but was determined not to be an economic pest in the absence of CLas. The HLB pathogen was first validated in FL in 2005, from an apparent “suitcase” importation of budwood, and likely was already widespread in south Florida from ACP feeding. The pathology community emphasized control through clean nursery stock (already in place), vector control, and roguing of infected trees. Initial efforts to rogue in south Florida revealed that a high proportion of trees were already infected and the epidemic was in exponential growth. A few growers decided that roguing would put them out of business and developed cultural practices to sustain infected trees. Almost the entire industry quickly followed suit, even in orchards hundreds of miles from the nearest established infections. The industry and associated research bodies quickly leveraged additional funds, and engaged the National Academy of Sciences and other bodies to identify research priorities. Some estimates suggest that a billion U.S. dollars have been spent on the disease, including all salaries and infrastructure. Tremendous progress has been made in understanding the HLB pathosystem, and FL oranges which had appeared to be doomed, can know be sustained at about 60% of the production expected from healthy trees, but at much greater production costs. Direct industry losses are estimated in the billions U.S. dollars, and overall economic impact substantially higher. Loss of acreage exceeds 180,000. Arguably, progress in understanding HLB has greatly benefited Texas, though the disease is now widespread there, and California where HLB finds have been restricted to several thousand dooryard trees, and ACP containment has kept ACP out of the Central Valley. After fifteen years of endemic HLB in FL, this is a good time to consider how we might better prepare for and address emergent diseases in the future. In retrospect, there is some discussion that funding more foundational work was neglected due to a focus on rapid solutions. Throughout the US experience with HLB, there has been discussion that conventional organizational and funding structures might be impediments, and a “Manhattan Project-like” approach may provide more rapid results. Other ideas and observations will be discussed in this workshop.