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Management of Citrus Greening and Virus Diseases for the Rehabilitation of the Citrus Industry in the ASPAC Region

FFTC has initiated work on rehabilitating citrus orchards in the tropics since the early 1990s, based upon an extensive survey on various citrus orchards in the Asian and Pacific (ASPAC) region. Most of the citrus orchards surveyed were severely suffering from systemic virus diseases, and the virus-like disease known as citrus greening (HLB). These diseases are easily transmitted to spread throughout the orchard, either by insect vectors or through vegetative propagated seedlings, thus being highly infectious and incurable. The orchard once infected could be only rehabilitated by clearing the infected trees and replanting pathogen-free healthy seedlings.

In view of the major devastation that these diseases have caused on the citrus industry in the ASPAC region, FFTC has since been working to address this issue by collecting relevant information, development of key technology, disseminating important technological information and transfer of promising technology. For instance, three key technologies for the orchard rehabilitation have been established based upon Taiwan's long-term experience and efforts. These are the cultivation of pathogen-free seedlings, elimination of inoculum sources, and prevention of secondary spread by vector insects. Establishment of pathogen-free nursery system is primarily important to prevent prevalence of these diseases. Precise and rapid disease-indexing techniques are indispensable for the management of the said nursery.

FFTC first conducted an integrated technology transfer program composed of the pathogen-free nursery system, net-house and demonstration orchard at the Plant Protection Research Institute (PPRI), Hanoi, Vietnam in 1997. As of the end of 2006, Vietnam has expanded the rehabilitated acreages to 2,000 ha in northern Vietnam provinces alone.

In spite of the great success in northern Vietnam, citrus greening and virus diseases are widely spreading in southern Vietnam without effective treatments. The epidemic of these diseases has become more common and widely spreading toward the inland of Cambodia. As high as 80 percent of the citrus orchards in these areas have already been infected by the diseases according to a survey conducted in 2006. In early 2007, FFTC has started a rehabilitation program of infected orchards in the campus of the Royal Agricultural University, Cambodia by establishing a pathogen-free citrus germplasm repository and training the experts on disease-indexing and pathogen-free seedling preparation.

Recently, various sophisticated technologies have been applied to biological characterization and pathogenecity of greening and virus strains collected from Taiwan and other Asian countries, under the joint FFTC/NIFTS/NTU project, and great progress has been made in further characterization and differentiation of the HLB isolates. New technological information obtained by the latest advanced analytical techniques greatly help scientists and extension experts develop more effective and stable counter measures against the systemic citrus diseases. Further studies are urgently needed in: a) improvement of HLB and virus detection methods; b) characterization of HLB strains by biological assay and molecule level; c) physiological studies on vector psyllid; d) eradication of HLB inoculum sources; e) production of pathogen-free citrus saplings; f) HLB-resistant citrus cultivars.


This training workshop aims to provide a forum to share the successful experiences, and exchange promising and practical technologies among experts from research institutes/agencies, and familiarize the participants with a holistic managerial approach as to rehabilitation of disease-infected orchards with pathogen-free seedlings and careful post-replanted management. Specifically, the workshop shall seek to:

  1. To develop a holistic technological package (and practical handbook) for the rehabilitation of infected orchards by systemic HLB and virus diseases in the ASPAC region;
  2. To disseminate and transfer relevant technologies to manage HLB- and virus infected orchards based upon the technological package (practical handbook) and on-bench and on-site demonstration; and
  3. To share and exchange relevant practical technologies and workable extension schemes to facilitate the rehabilitation management of the infected orchards in the ASPAC region.

Expected outputs

A practical handbook /resource manual shall be compiled to facilitate information dissemination and technology transfer as to the rehabilitation of HLB- and virus-infected orchards. The practical handbook will redound to more benefits for the disease-inflicted orchard owners and small- and medium-scale citrus farmers. Both resource and country report speakers will provide information on a variety of health management technologies for the rehabilitated orchards, while training courses or field demonstrations will emphasize on some simple and practical techniques on infection identification, virus indexing, chemical application, and other important issues on combating the citrus greening disease epidemics.

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