Grapevine Red Blotch detections
Industry Notice: 25 September 2022
Grapevine Red Blotch Virus (GRBV) has been detected in Western Australia, South Australia, and Victorian germplasms. Victoria will not be regulating GRBV although good hygiene practices are advised.
About GRBV
Grapevine Red Blotch disease, caused by GRBV, can reduce an infected vine’s capacity to move sugar from the vine leaves into the grapes. This sugar remains trapped in the leaves, consequently causing delayed fruit maturity, lower sugar, and compounds responsible for wine colour, flavour and aroma.
GRBV has not been reported to kill grapevines, but it can decrease the lifespan of a vineyard given lower yield and vine vigor and can negatively impact grape and wine quality.
Current situation
GRBV has been detected in WA, SA and germplasm in Victoria. GRBV has been detected in white table grape Perle de Csaba and several wine grape varieties.
There has been no known reports of visual symptoms of GRBV in vines that have recently tested positive in Australia.
Symptoms
In red varieties, foliar symptoms of GRBV consist of crimson to purple blotches first appearing on older leaves at the base of the canopy in late spring to early summer. These red blotches then expand and merge and become progressively evident towards the top of the canopy later into autumn.
In white varieties, leaf symptoms appear as irregular chlorotic (yellow) areas that become necrotic (dead) later in the season.
Some varieties infected with GRBV have been reported to show no visual symptoms.
There are many causes of red leaves in vineyards, including mechanical damage, nutrient deficiency (potassium, magnesium, phosphorus), variety specific autumnal colours, physical restrictions (string or ties), and other viruses such as leaf roll, which we already have in Australia. It is noted from overseas experience that GRBV is often reported in the presence of other viruses that we have in Australia. Confidence of diagnosis can only be obtained by laboratory diagnosis such as through Crop Health Services.
Distribution and spread
GRBV was first discovered in 2008 on Cabernet Sauvignon located in the Napa Valley, California. GRBV has been detected in commercial vineyards in the USA, Canada, Argentina, India, Mexico and South Korea. In Switzerland, France and Italy, GRBV has only been detected in non-commercial collections.
Long-distance spread of GRBV occurs through infected planting material. GRBV is not considered to be spread by vineyard machinery or pruning tools in countries where it is established.
We are yet to understand the ability of sap sucking insects in Australia, including scale, mealybug, and hoppers, to spread GRBV between vines.
Management and good hygiene
Maintain good general virus preventative management programs, including sourcing virus free propagation material and regular vineyard monitoring for virus-like symptoms and potential vectors.
For further information, please contact Agriculture Victoria via telephone on 136 186.
Printable copy
Please download a copy of this notice for printing