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Virus & Virus-like?

Virus & Virus-like?. Graft transmissible; Some vectored (insect, mite, fungus); Some mechanical True viruses Viroids Procaryotes Unknown. Major Citrus Virus & Virus-like Agents/Vectors. Tristeza Quick decline; stem pitting - Citrus tristeza virus /Aphids

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Virus & Virus-like?

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  1. Virus & Virus-like? Graft transmissible; Some vectored (insect, mite, fungus); Some mechanical True viruses Viroids Procaryotes Unknown

  2. Major Citrus Virus & Virus-like Agents/Vectors • Tristeza Quick decline; stem pitting - Citrus tristeza virus /Aphids • Huanglongbing (Greening) - Liberibacter spp./ Psylla • Psorosis/Scaly bark- Citrus psorosis virus/ Fungus? • Stubborn - Spiroplasma citri / Leafhoppers • Leprosis -Citrus leprosis virus / Mites • Variegated chlorosis- Xylella fastidiosa / Sharpshooters • Witches’ broom of lime - Phytoplasma / Leafhopper • Blight – cause / vector unknown • Exocortis - Citrus exocortis viroid / Mechanical • Cachexia - Hop stunt viroid / Mechanical • Tatterleaf – Citrus tatterleaf virus / Mechanical

  3. Other Virus & Virus-like Diseases • Concave gum, Cristacortis, Impietratura • Infectious variegation, Leaf rugose • Vein enation/Woody gall (Aphids) • Satsuma dwarf, Citrus mosaic (soil vector?) • Citrus yellow mosaic (Mealy bugs) • Dweet mottle (= Citrus leaf blotch?) • Rubbery wood • Multiple sprouting • Measles • Chlorotic dwarf (Whitefly) • Indian ringspots + other ringspot diseases • Concentric ring blotch/Zonate chlorosis (mites) • Gum pocket, gummy bark, Kassala • Corky vein • Yellow vein clearing/ Yellow mottle • Australian decline (leafhopper?) • Sudden death – NEW – SERIOUS (aphids?) Etc.

  4. History of Major Diseases • 1880’s - yellow shoot disease (HLB, greening) - China • 1890’s - blight - Florida • 1890’s - sour orange rootstock problems - South Africa • 1896 - psorosis described – Florida • 1930s – tristeza disease in S.America • 1934 - psorosis graft transmitted - Florida • 1943 - HLB graft transmitted - China • 1946/48 - aphid & graft transmission of tristeza - Brazil • 1965 - psylla transmission of HLB - South Africa • 1988 - graft transmission of blight - Florida

  5. Brown citrus aphid

  6. Acknowledgement ;Tim Gottwald

  7. Tristeza destruction of trees on sour orange rootstock • South America – approx. 40 million killed since 1930 (BCA) • Spain – 45 million since 1960 (No BCA) • Florida – 3 million in 2000-02 • Total worldwide – over 100 million • Italy – 98% on sour – decline widespread (No BCA) • 200 million to go? (TX, Mex., Med.)

  8. Exocortis

  9. Cachexia

  10. Psorosis

  11. Psylla

  12. Tatterleaf

  13. Blight

  14. Witches’ broom disease of lime

  15. Citrus variegated chlorosis

  16. Control • Prevention : - Used certified disease-free bud/graftwood - Quarantine - Prevent mechanical spread- chlorox disinfection - Mild strain protection (eg CTV) • Vector control ? Difficult to get 100% (eg. Biocontrol of psylla in Reunion)

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