How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS AND SIGNS

Eutypa dieback delays shoot emergence in spring, and causes shunted shoots and leaves that are chlorotic, tattered, and cupped. Symptoms in the wood are characterized by darkened cankers that develop in the vascular tissue. The cankers are often wedge shaped (like a pie chart) in cross-cuts of affected cordons or trunks. Cankers develop faster in the direction of the roots than toward the end of cordons. Extensive infections lead to vine death.

COMMENTS ON THE DISEASE

Eutypa dieback is not generally visible in vines younger than 5 to 6 years old although vines may still be infected. The disease is most easily seen in vines established for 10 or more years. The fungus survives in diseased wood and produces perithecia in old, infected host tissue under conditions of high moisture. In California several plants in addition to grape serve as reservoirs for the pathogen including almond, apricot, blueberry, cherry, crab apple, Ceanothus spp., kiwi, pear, oleander, and native plants including California buckeye, big leaf maple, and willow. Ascopores are discharged from perithecia soon after rainfall. Infection occurs through pruning wounds, which remain susceptible much longer early in the dormant season than later in the dormant season. Overall susceptibility is about 6 weeks.

MANAGEMENT

Prune late in the dormant season to promote rapid healing of wounds. Remove and burn infected wood inside the vineyard and dead wood in adjacent vineyards and orchards to reduce the spread of the pathogen. Cut out and remove dead arms and cordons from the vineyard during dormancy. Completely remove all cankers, pruning below the canker on the vine or trunks until no darkened canker tissue remains. Make large cuts directly after a rain because the risk for infection is lowest at this time, as the atmospheric spore load has been washed out temporarily (or is at its ebb). Double pruning cordon-trained vines can help final pruning cuts to be made quickly and late in dormancy, thus reducing the chance for infection. For additional protection, consider treating pruning wounds.

In table grapes, note locations in the vineyard with poor budbreak in spring. Examine these areas in fall for disease damage. Mark locations of vines with poor growth for future confirmation and management.

Common name		Amount/Acre**	R.E.I.+	P.H.I.+
(trade name)			(hours)	(days)
When choosing a pesticide, consider efficacy and the general properties of the fungicide as well as information relating to environmental impact.
A.	THIOPHANATE-METHYL
	(Topsin-M) WSB	1%	7 days	NA
	MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
	COMMENTS: Mix as a 1% paste and apply to cut or pruned surfaces immediately after cutting. Use allowed under a Special Local Needs label.
**	Apply with enough water to provide complete coverage.
+	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
1	Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different Group number are suitable to alternate in a resistance management program. For more information, see http://www.frac.info/.
NA	Not applicable.

PUBLICATION

UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448
Diseases
W. D. Gubler, Plant Pathology, UC Davis
R. J. Smith, UC Cooperative Extension, Sonoma County
L. G. Varela, UC IPM Program, Sonoma County
S. Vasquez, UC Cooperative Extension, Fresno County
J. J. Stapleton, UC IPM Program, Kearney Agricultural Research Center, Parlier
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley
Acknowledgment for contributions to Diseases:
G. M. Leavitt, UC Cooperative Extension, Madera County

Top of page