ARS | Publication request: CURRENT EPIDEMIOLOGICAL UNDERSTANDING OF CITRUS HUANGLONGBING

Submitted to: Annual Review of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 10, 2010
Publication Date: August 10, 2010
Citation: Gottwald, T.R. 2010. CURRENT EPIDEMIOLOGICAL UNDERSTANDING OF CITRUS HUANGLONGBING. Annual Review of Phytopathology. 48:119-139.

Interpretive Summary: Citrus huanglongbing (HLB) is a serious bacterial disease of citrus that I was first discovered in the Western Hemisphere in 2004. Since then it has been found in Florida, Brazil, throughout the Caribbean, and a few places in Central America including Mexico. Nowhere in the world with this disease occurs is it under adequate control. Therefore it is a great threat to the citrus industries of the United States. This article is a review of the current understanding of the epidemiology of HLB, that is it characterizes the current knowledge of how the disease increases and spreads with examples from throughout the world. Intent of the article is to compare the disease that is currently in the Western hemisphere and specifically in Florida with the rates of increase and spread from the literature in other places around the world. Detection, crop loss, and the current strategies for the most efficacious control our also discussed. The most recent control strategy is the use of statewide surveys and areawide control of the insect vector, and timely removal of infected trees. Also discussed are the implications of the latency of the disease, that is, the time during which the disease is infecting the tree and can be transmitted from a tree but is not yet showing symptoms. This is a very difficult stage of the disease to detect them greatly complicates control. This review serves as a knowledge base for all researchers and commercial industry to better understand the implications of this disease and its epidemiology.

Technical Abstract: Huanglongbing (HLB) is the most destructive citrus pathosystem worldwide. Previously known primarily from Asia and Africa it was introduced into the Western hemisphere in 2004. All infected commercial citrus industries continue to decline due to inadequate current control methods. HLB increase and regional spatial spread, related to vector populations, are rapid compared to other arboreal pathosystems. Disease dynamics result from multiple simultaneous spatial processes suggesting that psyllid vector transmission is a continuum from local area to very long distance. Evolutionarily, HLB appears to have originated as an insect endosymbiont that has moved into plants. Lack of exposure of citrus to the pathogen prior to ~ 100 years ago, did not provide sufficient time for development of resistance. Prolonged incubation period and regional dispersal make eradication non viable. Multiple asymptomatic infections per symptomatic tree, incomplete systemic distribution within trees, and prolonged incubation period, make detection difficult and greatly complicate disease control.