How to Manage Pests
UC Pest Management Guidelines
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.
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.
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.
UC IPM Pest Management Guidelines: Grape