Eurofins STA Today - Mar 2012
Grapevine Disease Spring Season Guidelines
for the Vineyard
By Judit Monis, Ph. D
This is the time growers are busy
planning new plantings and/ or
completing pruning and top working
activities. This article will focus on
testing and management strategies in
the vineyard that can help control the
establishment and spread of diseases.
As always our customer service goal
is focused on educating our clients
to understand plant health issues as
they relate to their vineyards. Our
newsletter articles are a tool to deliver
helpful tips on disease management
and control. To complement the
written articles we recently started a
new method of education through
the delivery of webinars (seminars
that are delivered via internet). If you
missed any of these events, the webinar
recordings are available for viewing at
our website (http://www.eurofinsus.
com/stalabs/products-servicesgrapevine-testing.html). The recordings
can be downloaded (both in English
and Spanish) for a limited time (all
webinars expire one year after the initial
presentation).
The most important step to establish
a healthy vineyard is the planting
of pathogen-free material. Many
diseases are graft transmissible and
once established in the vineyard there
is no cure. However, it is important
to understand what is causing the
problem as specific management
practices can help growers control
the spread of pathogens (disease
causing agents) in the vineyard or to
neighboring vineyards.
Assessment of the health status of
scion and rootstock planting selections
is a crucial step in ensuring a healthy
vineyard and consequently a successful
vintage. Many growers rely on planting
“healthy looking” material from their
own or neighboring vineyards. Derived
vines should be planted with caution
as vines can harbor pathogens without
showing notable signs of infection. To
insure disease-free stock, representative
samples should be submitted to our
laboratory to test for major diseasecausing agents (i.e., viruses, bacteria,
and fungi). To assure the highest
quality, planting material from certified
sources must always be tested as our
experience has shown that it is possible
to detect pathogens in such stock.
Top working, an activity used in the
vineyard to quickly change the scion
variety, allows sampling the most
mature sections (cordon and trunk) of
the vine. The portions above and below
the graft union constitute the best type
of sample for testing for the presence
of fungal pathogens (vine decline, Bot,
Eutypa, or other canker causing fungi)
and viruses included in HealthCheckTM
Panel A (leafroll and rugose wood
diseases). Root samples are required
to detect the presence of soil-borne
pathogens.
The ideal sample number to test prior
to making top grafting decisions
will depend on the diversity of vines
present in the vineyard. If the vineyard
is planted with vines from the same
origin (i.e., same rootstock/scion
combination from a common source)
testing at least five vines for the
presence of viruses is recommended.
If there are many rootstock/scion
combinations, the vines are from
unknown origin, there is suspicion of
infection, or the vineyard is adjacent to
an infected vineyard, a more exhaustive
sampling regime will be required. Our
lab does not recommend compositing
many vines into one
sample. Furthermore, the number
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Grapevine Disease Spring Season Guidelines for the Vineyard Continued
of vines to sample will increase if
mealybugs, nematodes, or other
disease transmitting vectors are present
in the target vineyard or neighboring
vineyards. If disease symptoms are
present in the vineyard, the samples
from the most symptomatic vines
should be submitted for testing. If
no apparent symptoms are present,
random and representative sampling is
recommended.
Because of the potential of virus spread
and bacterial (i.e., crown gall disease)
and fungal infections in vineyards it is
important to test samples after nursery
grafted plants have been finished in the
field. In many cases these plants will
be stored in the cold before planting.
Subjecting bench grafts to fungal
pathogen testing after cold storage is
strongly recommended. The testing
is needed even if the vines are from a
reputable certification program.
correctly planted in the ground and
be provided with the right amount of
water and nutrients. New plantings
should be allowed to establish in the
vineyards prior to heavy cropping.
Some viticulturists recommend at least
three years without grape production
to allow sufficient nutritional reserves
in the vine. Many of the fungi that
cause disease in grapevines are
endophytic (i.e., can happily live in
the vine without causing disease)
but become pathogenic in the
presence of any stress (i.e., grafting,
drought, salinity, overwatering, poor
planting, etc.). Double pruning and/
or late pruning are practices that are
recommended for vineyards that are
affected by Botryosphaeria, Eutypa,
and other canker producing fungi.
The pruning is carried out as late as
possible but before bud break. The
practice assumes that fungal spores
have been depleted and are no longer
available to start new infections in
the vineyard. The use of special paints
and or chemicals (i.e., fungicides) can
protect the pruning wounds from new
infections. In all cases it is important
to remove pruning clippings and plant
debris from the vineyard. Research has
shown that training a new growth from
the scion with subsequent removal of
a dead arm as soon as the new growth
is established (surgery practice) can
extend the life of a vineyard affected by
canker causing fungi.
Just as important as knowing the
health status of the planting material
is exercising caution when planting
and managing the vineyards. For
optimum results, the vines must be
For non-destructive testing, samples
will need to be submitted at different
times of the year to cover the whole
spectrum of grapevine disease causing
agents. For example, the Pierce’s
The best time to submit samples for
disease testing of planting material
should coincide with the time the
grower decides which rootstockscion combination will be used in the
vineyard. In most cases, nurseries are
able to trace their mother vines and
organize cuttings from specific blocks.
A representative sample should be
collected from each block (or bin) of
rootstock and scion material that will be
used for grafting.
Disease bacterium is best detected
later in the summer season (petioles
from mature leaves), while the viruses
associated with decline are best
detected in the spring season (young
foliar shoots). Our testing guidelines
indicate that the spring season is the
most appropriate time for submission
of samples for HealthCheckTM Panel
B, CG and Fungal Panel However,
growers can continue to send material
for HealthCheckTM Panel A testing if a
representative sample consisting of a
portion of lignified cordon
and/ or trunk are provided. Much more
information on disease testing can be
found in our recorded webinars and our
website.
Please contact Judit Monis (888782-5220 or juditmonis@eurofinsus.
com) if you would like to discuss the
information or have questions about
our grapevine disease testing program.
STA Laboratories
Colorado Laboratory
1821 Vista View Drive
Longmont, Colorado 80504
(303) 651-6417
Gilroy Laboratory
7240 Holsclaw Rd.
Gilroy, CA 95020
(408) 846-9964
www.eurofinsus.com/stalabs
[email protected]