Virus & Virus-like? Graft transmissible; Some vectored (insect, mite, fungus); Some mechanical True...
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Transcript of Virus & Virus-like? Graft transmissible; Some vectored (insect, mite, fungus); Some mechanical True...
Virus & Virus-like Diseases ofCitrus & Avocado
John V da GracaTexas A&M University-Kingsville
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
• 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
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.
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
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.)