Eutypa dieback is caused by the fungus Eutypa lata and is one of the major trunk diseases of grapevines.
Eutypa occurs worldwide in wine regions that exceed an annual rainfall of 350mm. In Australia, eutypa was first detected in the 1930s and, apart from Western Australia, is now widespread, having a significant impact on the productivity and profitability of viticulture in this country. All major grapevine varieties grown in Australia are susceptible to eutypa infection. In South Australia, eutypa dieback is most pronounced in Shiraz, Cabernet Sauvignon and Grenache. The varieties Riesling and Merlot are less susceptible to the disease.
Grapevines can become infected by eutypa through fresh cuts, such as those made during pruning or reworking, and is spread by airborne spores which are released from infected dead wood during rainfall. Spores infect exposed pruning wounds, with vines being most susceptible to infection in the first two weeks after pruning. The fungus grows slowly, causing stunted shoots and progressively killing spurs, cordons and trunks and eventually the entire affected vine.
Wedge-shaped zone of dead wood as a result of eutypa infection.
Foliar symptoms of eutypa infection may not develop until 3-8 years after infection and are often only apparent on one cordon of an infected vine. Eutypa dieback is most obvious in spring when shoots are 30 to 70cm long (EL 12 – 17). Inspections after this timeframe can be more difficult, as canopy growth often conceals symptoms. Shoots appear stunted and the leaves yellow, often becoming cupped and tattered around the edges. Grape bunches on infected shoots ripen unevenly, are small and in severe cases shrivel and die. Cross-sections of cordons with stunted shoots reveal characteristic dark brown, wedge-shaped zones of dead wood. These zones can be traced back to cankers, which are sunken dead areas on the outside of cordons and trunks. Many years after infection, cordons begin to die and vines are killed when cankers girdle the trunk.
Yield losses are related to the severity of foliar symptoms, with losses up to 1500kg/ha reported in severely-affected red wine varieties. Vineyard productivity is also affected by eutypa dieback, with increased production costs and decreased vineyard longevity. In addition, uneven bunch ripening can reduce the quality of the resultant wine. Disease control can be achieved with preventative wound treatments and curative remedial surgery to remove infected wood.
Experiences with eutypa dieback. Discover how vineyard owners across several South Australian grapegrowing regions are dealing with Eutypa dieback.
Managing eutypa dieback. Click here to access a video series by Clare Region Winegrape Growers Association, supported through the Wine Australia Regional Program for SA North.