North American Grapevine Yellows (GY) is a lethal disease of winegrapes causing yellowing of leaves, die back of shoot tips and fruit abortion. Infected grapevines often die within months of the onset of symptoms and significant losses of vines have been observed. In Virginia, aster yellows and X disease phytoplasmas have been detected in infected winegrapes. Phloem-feeding leafhoppers, planthoppers or, occasionally, psyllids are vectors of other phytoplasma-caused plant diseases, including European grapevine yellows. Hence, one or more insect vectors are suspected of transmitting GY phytoplasmas to winegrapes in Virginia.
Using sweep net sampling and yellow sticky traps, surveys of potential vector species in and around infected vineyards were made in 2002 and 2003. Insects were assayed for the presence of GY phytoplasmas by polymerase chain reaction (PCR). In 2002, twelve leafhopper species and one planthopper species tested positive for aster yellows phytoplasma; two leafhopper species tested positive for X disease phytoplasma.
Because phytoplasmas have been detected in non-vector insect species, transmission experiments using commonly observed candidate vector species were initiated to determine which could acquire and transmit GY phytoplasma. Three leafhopper species transmitted phytoplasma to indicator faba bean plants; one species transmitted phytoplasma to a test Chardonnay plant.
Membrane feeding trials also were performed to determine which candidate species introduced phytoplasmas along with saliva into Tris-EDTA-sucrose (5%) solutions during feeding. Five leafhoppers species introduced aster yellows phytoplasma into test solutions.
Species 1: Homoptera Cicadellidae (leafhopper)
Keywords: Grapevine Yellows
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