EUTYPA DIEBACK
Description
Symptoms
Disease Cycle
Control

Description:
Eutypa dieback is a fungal disease of woody grape tissue caused by Eutypa lata that attacks grapevines all over the world. The fungus usually enters the vines through pruning wounds, causing dieback of spurs and arms, and eventually the death of the vine. Prior to 1976, researchers thought that “dead-arm” disease was caused by the fungus Phomopsis viticola, but it was later demonstrated that the “dead arm” disease is actually two different diseases occurring simultaneously. Eutypa dieback is now used as the name for the trunk and arm phase of what was once called “dead-arm” and Phomopsis canker is the disease name for the shallow cankers associated with infections by P. viticola.

Symptoms:
The earliest symptom of the disease is a canker that initiates around the pruning wound in older wood on the main trunk. In a cross section of the trunk, the canker appears as dark “V” shaped wood extending to the center of the trunk. The vascular system is never invaded entirely in the cross section. During spring, the young shoots that grow upstream to the diseased wood show stunted growth (Fig.1) and later in the season the leaves become scorched and tattered (Fig.2). These symptoms are primarily due to the presence of the toxin eutypine produced by the fungus and transported in the vascular system.

Disease Cycle:
The fungus survives in cankers for long periods of time and produces fruiting structures (perithecia) within the cankers that discharge ascospores during rainy periods in the late winter or early spring. These spores are dispersed in rainwater or are airborne and deposited on pruning wounds-- the principal infection sites.

Control:
Cultural - Sanitation is very important in minimizing infection. All dead wood (cordons) from infected plants should be removed from the vineyard and destroyed. The time of pruning is critical. If a vineyard has a history of Eutypa dieback, pruning should be delayed as long as possible. There are some differences among cultivars in their susceptibility; Sauvignon Blanc and Cabernet Sauvignon are considered to be more susceptible than Merlot, Semillon and Chardonnay.

Chemical- Currently there is no fungicide registered for control of the disease (Table 1).