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CITRUS GREENING DISEASE

CITRUS GREENING DISEASE. Presentation by Dr. Jamba Gyeltshen, 4/06/09. SYNONYMS FOR GREENING DISEASE. South Africa Greening Yellow branch Blotchy mottle China Yellow shoot (Huanglongbing) Taiwan Decline (Likubin) India Die-back The Phillippines Leaf mottle Indonesia

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CITRUS GREENING DISEASE

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  1. CITRUS GREENING DISEASE Presentation by Dr. Jamba Gyeltshen, 4/06/09

  2. SYNONYMS FOR GREENING DISEASE • South Africa • Greening • Yellow branch • Blotchy mottle • China • Yellow shoot (Huanglongbing) • Taiwan • Decline (Likubin) • India • Die-back • The Phillippines • Leaf mottle • Indonesia • Vein phloem degeneration

  3. CAUSAL ORGANISM Two ‘Candidatus Liberobacter spp.’ • Liberobacter asiaticum • Liberobacter africanum Candidatus in scientific classification is a formal word that is placed before the genus and species name of bacteria that cannot be maintained in a Bacteriology Culture Collection. Such type of bacteria are also known as fastidious bacteria (nonculturable). Their low concentration and uneven distribution presents difficulties to detect by conventional methods

  4. DISTRIBUTION • Spread over 24 other countries in Asia and Africa • In the recent years it has been confirmed in the Americas: Brazil and USA (Florida) • No confirmed report from middle East and North Africa

  5. ECONOMIC IMPORTANCE • Losses difficult to estimate; sometimes small, sometimes total loss; South Africa 30-100% crop losses recorded in some areas.

  6. SYMPTOMS • First symptoms- yellowing along the veins or blotchy mottle • Sometimes chlorotic mottle resembling zinc or iron deficiency • Lopsided fruit that are bitter in taste and have aborted seeds • Premature fruit drop • Green color retention at maturity

  7. Leaf symptoms • Pummelo (top): yellowing, mottling, and vein corking • Sweet orange (middle): small in size and showing symptoms of zinc deficiency (3 leaves); mature, mottled leaves which are curling outwards • Mandarin: yellowing and mottling • http://www.fftc.agnet.org/library/image/tn2001002f1.html

  8. Symptoms on fruits • Diseased twig with yellow leaves and diseased fruit of Tankan tangor. (left): the fruit is small and pale green in color. A healthy green leaf and normal large fruit are shown to the right.http://www.fftc.agnet.org/library/image/tn2001002f4.html

  9. SYMPTOM VARIATION • In Asia: extensive yellowing, dieback, and decline • In China young trees have been killed in 1-2 years. • Root systems remain poorly developed with relatively few fibrous roots • New root growth suppressed and roots often start decaying from the rootlets.

  10. TRANSMISSION • Experimentally transmitted by dodder to periwinkle (Cantharus roseus) • Consistently transmitted via grafts but not through budding • Insect vectors: psyllids

  11. The Asian citrus psylla • Fig. The Asian citrus psylla Diaphorina citri, which transmits the Asian strain of the greening organism

  12. Life History • Eggs hatch in about 2-4 days. A female lays up to 800 eggs during her lifetime of several months. There are five nymphal instars. The complete life cycle ranges from 2 to 9 weeks depending upon food and temperature. This may result in up to 30 overlapping generations per year in hot climate. • http://ipm.ifas.ufl.edu/agricultural/fruit/citrus/ASP-hoy.htm

  13. Asian psyllid • Diaphorina citri – heat tolerant • psyllids can carry the pathogen throughout their adult life; lifespan=90 days • 100% transmission when feeding for at least 1 hr • PCR assays +ve 2 months after inoculation • Symptoms developed 8 months after inoculation • (Hung et al., 2001)

  14. African citrus psyllid • Trioza erytreae -heat sensitive • no symptoms appear above 30 deg. C • 32 deg. C all stages killed (lab tests); • 27 deg. C 52% mortality • 21 deg 9% mortality • requires 1 day feeding; latent period 7 days • 4% new trees affected per day (Hung, et al., 2004)

  15. Disease management • Once infected, it is difficult to control • Control of vectors • Healthy propagating materials • Quarantine

  16. REFERENCES • da Graca J. V. 1991. Citrus greening disease. Annual Review of Phytopatholgy 29:109-136. • Hung, T. H., S. C. Hung, C. N. Chen, M. H. Hsu, and H. J. Su, 2004. Detection by PCR of Candidatus Liberibacter asiaticus, the bacterium causing huanglongbing in vector psyllids: application to the study of vector-pathogen relationships. Plant Pathology 53: 96-102. • Hung, T. H., M. L. Wu, and H. J. Su, 1999. Development of a rapid method for the diagnosis of citrus greening disease using the polymerase chain reaction. J. Phytopathology 147:599-604. • Jagoueix, S., J. M. Bové, and M. Garnier. 1996. PCR detection of the two ‘Candidatus’ liberobacter species associated with greening disease of citrus. Molecular and cellular probes 10:43-50. • Knapp, J. L., S. Halbert, R. Lee, M. Hoy, R. Clark, and M. Kesinger, 2004. Agricultural IPM: Fruit (Citrus):The Asian Citrus Psyllid and Citrus Greening Disease. IFAS, University of Florida. IPM Florida website http://ipm.ifas.ufl.edu/agricultural/fruit/citrus/ASP-hoy.htm doi 11/21/04

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