Grapevine Red Blotch Disease Management in the Vineyard

Grapevine Red Blotch Disease Management in the Vineyard

Photo credit: Washington State University

Grapevine Red Blotch Virus (GRBV) can affect profitability of vineyards by up to $170,000 per acre over the lifespan of the vineyard. Many symptoms can result from GBRV depending on the varietal, but the fruit often show increased sugar and acidity which affects overall ripening and quality. Wine makers rely on the consistency their grapes for a balanced flavor profile, making GRBV infected grapes of no value in the production process.

While you can use services such as Pollen to detect diseased crops, specifically detecting GBRV can be challenging since many common symptoms are similar to grapevine leafroll virus and nutritional disorders, and the only valid method of testing is through polymerase chain reaction (PCR) in a laboratory setting. You also need to send your vegetative samples to a testing lab in the late summer to early fall, and your cane samples during the dormant period.

Preventing the spread of GBRV can be even more challenging and requires an in depth knowledge of disease ecology in vineyard ecosystems. Spatiotemporal models show that vines are more likely to infected by nearby infected vines than from an outside inoculum source, and the vectors of disease are usually insects. Studies also show that only four rare vineyard insect species tested positive for GBRV, including (Spissistilus festinus) or commonly known as three-cornered alfalfa hopper (TCAH), two leafhoppers (Colladonus reductus and Osbornellus borealis) and a planthopper (Melanoliarus spp.). Currently the only confirmed vector of GRBV is the TCAH.

Best practices recommend you scout for disease symptoms late in the growing season and send your samples to a lab for absolute diagnosis. To determine if GBRV is spreading in your vineyard, divide the number of infected vines by the number of inspected vines and compare the percentages over several years. An increase in infected vines over a two to five year period indicates you have spreading. Management recommendations should be considered along with the site-specific and regional conditions of your vineyard, and should only be considered a guideline for your disease management.

If the disease incidence in your vineyard or vineyard area is higher than 30%, you may need to move your vineyard to a different location. After lab confirmation of GBRV, consider removing virus inoculum sources that are close to new plantings. You may also want to remove wild vines from nearby forested areas once you are permitted by the Regional Department of Fish and Wildlife. If you suspect GBRV in your vineyard, start monitoring for TCAH to stay aware of any potential disease vectors.
To help streamline the scouting process and detect disease earlier in the growing season, Pollen Systems provides aerial NDRE imaging and monitoring services. Late in the growing season, vineyards can direct scouting efforts to areas more likely to be infected with with GBRV, leafroll and other diseases. NDRE is highly sensitive to chlorophyll levels and will detect underperforming (low NDRE values) areas that are more likely to be infected. To learn more about Pollen Systems solutions please view our other blogs at http://www.pollensystems.com/news-updates/

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