The Crush - September 2020 - 1

theCrush
Volume 47 Issue 9 September 2020

[ FEATURE STORY ]

Grapevine Virus and Vector Management
UPDATE ON NEW TOOLS, RESOURCES, RESEARCH
By Ted Rieger
Grapevine viruses, notably grapevine leafroll associated virus
(GLRaV) and grapevine red blotch virus (GRBV), and mealybug
vectors, continue to be major issues for California grape growers
due to their significant economic impacts on vine health and
vineyard lifespans and effects on reducing winegrape yield and
quality.
NEW VIRUS WORKBOOK FOR GROWERS
Additional tools and resources to better understand and manage
viruses and vectors have become available. Also, new and
ongoing outreach, research and area-wide grower programs will
provide more resources moving forward. A project to expand
grower outreach and develop virus best management practices
reached a major milestone this year with the release of a 138-page
workbook, "What Every Winegrower Should Know: Viruses."
The project has been promoted since 2016 by CAWG member
and director Aaron Lange of LangeTwins Family Winery and
Vineyards and implemented by the Lodi Winegrape Commission
(LWC).
Outreach activities and production of the workbook were
coordinated by LWC Research and Education Director Dr.
Stephanie Bolton, with direction from the Lodi Grapevine
Virus Research Focus Group and the Lodi Mealybug Biocontrol
Research Focus Group. The project was supported with grant
funding from the American Vineyard Foundation (AVF) and the
California Department of Food and Agriculture's (CDFA) Pierce's
Disease/Glassy-Winged Sharpshooter Board.
Basic strategies recommended to reduce virus spread include:
Decrease vector populations, lower virus inoculum,
scout vineyards for mealybugs and for virus
symptoms, test symptomatic vines, rogue
individual vines that test virus-positive
when they make up 25 percent or less of the

vineyard, remove
the entire vineyard
if more than 25
percent of the vines
are infected, and
replant vineyards
with clean vines
that are virus-tested
from certified
nurseries.
The workbook
provides detailed
steps to guide
vineyard planning,
development,
Photo: Ted Rieger
monitoring and
management
in relation to viruses. Subjects covered include virus basics,
ordering nursery materials, mealybug management, virus testing
(including a step-by-step guide for collecting vine samples,
preparing them to deliver to the lab), a list of testing labs and
how to manage testing costs, infected vine removal/rogueing,
and sudden vine collapse. Grower case studies cover scouting,
mapping and rogueing vines; replanting following a leafrollinfected vineyard; and neighborhood communication (working
with neighboring vineyards to reduce spread risks and plan
management).
The workbook includes lists of insectaries for beneficial insects,
vendors of mealybug pheromone traps, a beneficial insect risk
chart to evaluate insecticide risks related to biocontrol, and
a laminated mealybug scouting card for field use. The LWC
is also providing custom printed rolls of flagging to use in
vineyards. A red roll of flagging with mealybug images is for
mealybug hotspots in vineyards to flag each vine identified with
a mealybug infestation. Growers can then monitor adjacent vines
The Crush - September 2020

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