The Crush_January_2023 - 1

Volume 49 | Issue 1 | January 2023
Grapevine Trunk Diseases and Management Practices
Article by Ted Rieger
Grapevine trunk diseases (GTD) are found in vineyards
worldwide and can severely impact vine health, crop
productivity and a vineyard's lifespan. They are caused
by a wide range of wood colonizing fungal pathogens.
Most GTD pathogens produce overwintering fruiting
structures on infected woody tissue that produce
fungal spores. In California, GTD spores are commonly
released during winter following precipitation events,
and can start vine infection through contact on pruning
wounds. Multiple fungal pathogens commonly exist
in infected vines and they can be difficult to identify
and control. While GTD infection can occur in young
vineyards as early as pruning begins, diseases can
take several years to develop before causing visible
symptoms and damage.
Common GTDs and their associated fungal pathogens
in California vineyards include:
* Esca, a vascular disease complex, also
called young vine decline, Petri disease and
black measles, caused by Phaeomoniella
chlamydospora and Phaeoacremonium
* Botryosphaeria dieback, or Bot canker,
caused by Neofusicoccum parvum and other
Botryosphaeriaceae family species.
* Eutypa dieback caused by Eutypa lata and other
Diatrypaceae species.
* Phomopsis dieback, and cane and leaf spot,
caused by Phomopsis viticola.
Early adoption of practices to
prevent GTD infection and spread
provide the most cost-effective
benefits over the life of the vineyard.
UC Cooperative Extension (UCCE)
plant pathologist Dr. Akif Eskalen,
based at UC Davis, recommends the following
* Use the cleanest plant material available when
planting new vineyards.
* Minimize stress conditions on young vines.
* Delayed or later season pruning can reduce
the period of potential infection after the main
rainy season, because fewer spores are present
and pruning wounds can heal faster with drier
weather and vine sap flow. Double pruning,
with a second later season pass, can also reduce
* Use sharp and efficient tools to make clean and
smooth pruning cuts to speed the callusing
process, and reduce the area for infection that
occurs with ragged cuts.
* Remove pruned and infected vine material
promptly from the vineyard to prevent
development of fungal fruiting structures.
* Apply pruning wound protectants (applied as
paint or spray applications) as soon as possible
after pruning to prevent new infections.
If symptoms are visible, diseased vine parts should be
removed by cutting below the infected wood. Eskalen
observed, " If you can catch the disease while in a spur
or cordon, you have a better chance of saving the
vine. Once it develops in the trunk it is more difficult to
maintain a healthy vine. "
Pruning wounds are the primary points of infection
for GTD pathogens. Eskalen said wounds can
be susceptible to infection for up to one month
depending on environmental conditions. It is best
to know the types (species) of fungal pathogens and
spores that are present in the vineyard to determine

The Crush_January_2023

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