The Lodi Winegrape Commission has been actively studying the California grapevine virus situation since 2017.  The Commission’s Research, Education, & Communications Committee has formed two teams which have been instrumental in gathering information, creating educational materials, and offering real-world, practical outreach for our winegrowing community: the Lodi Mealybug Biocontrol Research Focus Group and the Lodi Grapevine Virus Research Focus Group.

Grapevine viruses pose a severe threat to the sustainability of California viticulture.  Unfortunately, there is little faith in virus prevention at any level.  Growers are losing contract dollars as wineries reject grape loads due to virus-induced ripening problems.  The good news is that there are virus management strategies which growers can implement right now in the short-term, which can be taught through real-world, hands-on integrated outreach from a team of growers, extension personnel, PCAs, and scientists.  With the right communication, a long-term cooperative virus strategy can save the California industry from devastating future losses.

Both the Mealybug Biocontrol and the Grapevine Virus Research Focus Groups were funded via grants from the American Vineyard Foundation, and the Virus Focus Group is aided by additional funds from the CDFA PD/GWSS Board for a project titled “Grapevine Virus Management in Lodi: A Collaborative Research & Integrated Outreach Effort to Help Solve a Statewide Challenge.

To sign up for our new grapevine virus email list-serve, where you’ll be invited to all outreach events and given any important updates as they come along, send an email to Dr. Stephanie Bolton with the subject “virus email list subscribe.”

The Commission is happy to announce that Lodi is part of a CDFA BIFS project team looking at “Refinement and Implementation of an Areawide Program for Vineyard Pathogens and their Insect Vectors” and led by Dr. Kent Daane.  This project continues decades of work studying the regional management of mealybugs and leafroll virus in Lodi and the Central Coast.

OUTREACH VIDEOS

Below is a recording from the Lodi Mealybug & Virus Outreach Meeting on April 4th, 2019.  Speakers included Dr. Kent Daane (UCCE, vine mealybug expert), Dr. Marc Fuchs (Cornell Univ., grapevine virus expert), Prof. Gerhard Pietersen (South Africa, leafroll virus expert), and Dr. James Stamp (Stamp Associates, planting material expert).  There is a Q&A panel with the speakers, Chris Storm (Vino Farms, viticulturist) and Aaron Lange (LangeTwins, Vineyard Operations).  Funding for this meeting was provided by the American Vineyard Foundation, the CDFA PD/GWSS Board, the Lodi Winegrape Commission, and UCCE.  Over 250 people were in attendance and there are a lot of great take-home messages for virus management.

LEAFROLL VIRUS SPREAD VIDEO:


SUDDEN VINE COLLAPSE

As you are likely aware, we’ve been studying a mysterious vine collapse situation (happening mostly in San Joaquin, Stanislaus and Coastal Counties in California thus far) since around 2010.  Patches of grapevines collapse over time – some of the growers saw 30% of a vineyard block collapse within just two years.  The vines may show stunted shoots and they usually push out some fruit before collapsing.  We have seen this collapse happen mostly on Freedom rootstock, but we now have confirmed cases on O39-16 and 101-14 and there are likely other rootstocks affected as well.  Many tests were conducted over the years by several PCAs and researchers until in 2018 a local team started uniformly collecting case studies and testing the patches in a consistent manner.  This summer, Dr. Akif Eskalen and Dr. Maher Al Rwahnih came to Lodi to collect samples from four affected sites for high-throughput sequencing (HTS) to test for known viruses and any possible novel virus/es, and a thorough fungal analysis (partially funded by the Lodi Winegrape Commission).  Every collapsing vine tested positive for a leafroll virus and for a vitivirus. There were trunk disease pathogens isolated from each sample, but not the same ones.  We continue to collect case studies to investigate the potential role of leafroll virus and vitiviruses in the collapse disease complex. At this point, it is looking like a combination of a leafroll virus-sensitive rootstock, a leafroll virus, a vitivirus, and another stress (which could be possibly trunk pathogens, crop or water stress, etc.), leads to the collapse – which may be a form of virus-induced rootstock incompatibility.  Learn more at any CD11 LODI IPM NETWORK BREAKFAST meeting (held on the first Tuesday of every month, 8am, Burgundy Hall, Lodi Grape Festival Grounds) or the MEALYBUG & VIRUS OUTREACH MEETING on August 27, 2020. All are welcome.

Articles about the sudden vine collapse:


FURTHER READING

Here are some resources that we have found helpful as we’ve researched grapevine viruses:

If you have anything to add, please let us know!  Send a link to Dr. Stephanie Bolton, stephanie@lodiwine.com.


HANDOUTS FROM OUTREACH EVENTS


VIRUS GROWER WORKBOOK

As information becomes available, the Lodi Grapevine Virus Research Focus Group is creating draft booklets on different virus management topics.  These booklets are partially funded by the American Vineyard Foundation and the CDFA’s PD/GWSS Board.  We are publishing these draft booklets, along with more educational material, tons of photos, and case studies, into a VIRUS GROWER WORKBOOK to be passed out at the 2020 Mealybug & Virus Outreach Meeting.  Hard copies and flash drives will be available for FREE to those interested.


HELPFUL LINKS

  • CDFA’s current list of registered nurseries, which offer CDFA-certified virus-tested planting material
  • Prof. Gerhard Pietersen has fantastic, practical information on leafroll virus management in South Africa HERE
  • Click HERE for a list of grapevine virus resources, including commercial testing labs, mealybug biocontrol, and more (updated 1.2020)
  • USDA Farm Bill provides financial assistance for growers affected by red blotch and leafroll viruses *NEW* under the Tree Assistance Program (updated 10.2019)

IN THE PRESS