The Crush - January 2021 - 1

Volume 48 Issue 1 January 2021


Grapevine Trunk Disease Management

By Ted Rieger
Grapevine trunk diseases (GTDs), also called canker diseases, are
a problem in vineyards worldwide. More than 60 fungal species
are known to cause GTDs. Multiple fungal pathogens commonly
exist in infected vines and they can be difficult to identify and
control. Biological and chemical fungicides and sealants are
available, and more are being developed, to apply as pruning
wound protectants after dormant pruning. In addition, research
in California vineyards is underway to identify and test beneficial
microorganisms that provide natural defense mechanisms in
grapevines to prevent and inhibit GTD occurrence.
The more common GTDs and their associated fungal species
found in California vineyards are:
*	 Eutypa dieback (Eutypa lata and other Diatrypaceae species).
*	 Esca (a complex of fungi also known as black measles)
and Petri disease or young vine decline (Phaeomoniella
chlamydospora and Phaeoacremonium minimum).
*	 Botryosphaeria dieback or " bot canker " (Neofusicoccum
parvum and other Botryosphaeriaceae family species).
*	 Phomopsis dieback and Phomopsis cane and leaf spot
(Phomopsis viticola).
Most GTD fungal pathogens produce overwintering fruiting
structures on infected woody tissue. When conditions are
favorable, the fruiting bodies release fungal spores into the
environment that can start vine infection through contact on
pruning wounds.
A challenge with GTD management is that infection
can occur in young vineyards - as early
as pruning begins - but these diseases
can take several years to develop before
causing visible symptoms and damage.
Once symptoms occur, it is often too late to

Wedge-shaped cankers in vine cross sections.

save vines without performing significant " surgery " to remove
diseased wood. Symptoms include poor vigor, distorted leaves
and shoots, shoot and tendril dieback and berry specks. Wedgeshaped cankers in vine cross sections lead to spur, cordon and
trunk dieback and eventual vine death.
Early adoption of practices to prevent GTD infection and spread
provides cost effective benefits over the life of the vineyard. An
online trunk disease diagnostics app, an interactive economic
management tool to input data to make economic management
decisions, and other information on GTD management are
available on the SCRI Trunk Disease Project Page.
Dr. Akif Eskalen, UC Cooperative Extension plant pathologist
in the UC Davis Department of Plant Pathology, discussed
recommended GTD management practices during a recent
educational webinar presented by the Lodi Winegrape
Commission. He advised using the cleanest plant material
available when planting new vineyards and minimizing stress
on young vines after planting. Pruning cuts should be clean and
smooth to speed-up callusing at the pruning wound. Pruning

The Crush - January 2021

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The Crush - January 2021 - 1
The Crush - January 2021 - 2
The Crush - January 2021 - 3
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The Crush - January 2021 - 6
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