Eutypa dieback, caused by the fungus Eutypa lata, is a major disease of grapevines in Australia and worldwide. In 1999 the disease was estimated to cause yield loss of A$1-3,000 per hectare in Shiraz in South Australian vineyards and the cost to the Californian grapevine industry was estimated at US$260 million per annum. Eutypa dieback threatens the sustainability of premium vineyards, especially those 8 years or older, and is becoming an increasing problem in most cool climate growing regions of southern Australia. The fungus infects vines through pruning wounds, colonises wood tissue and causes a characteristic wedge of dead tissue. The fungus produces toxic metabolites which are translocated to the foliage, causing stunting of the shoots, distortion and necrosis of leaves, reduced bunch size and uneven ripening. If left unmanaged, the fungus eventually kills infected vines.
Between 1999 and 2006 the CRC for Viticulture and GWRDC funded the National Grapevine Trunk Disease project to examine ways of reducing the impact of trunk diseases in Australian vineyards. The main outcomes include:
Foliar symptoms of eutypa dieback were directly related to yield losses although symptom expression varied from year to year. New evidence suggests that environmental factors may contribute to this phenomenon.
The development of a bioassay where foliar symptoms are induced within 8 months and isolates of E. lata varied in their ability to induce foliar symptoms.
Remedial surgery was the most effective method for treating infected vines in the short-term (up to 5 years).
Chemical and biological alternatives have been evaluated for protecting pruning wounds from infection, and a number of effective methods can now be recommended to growers, with one product currently registered and several more in the process.
A DNA assay has been developed for the identification of E. lata in pure culture and in wood tissue, giving more accurate and potentially cost-effective results than morphological methods.
Growth of E. lata ranged from 10-18 mm per year in wood of various grapevine cultivars in the field.
Dr Philippe Larignon (ITV France), a leading French researcher in trunk diseases, recently stated that research towards alternative strategies against trunk diseases is strongly hampered by limited knowledge of the biology and epidemiology of these diseases and the need for long term studies, necessary to prove the efficiency of new strategies. At the 4th International Workshop for Grapevine Trunk Diseases in Jan 2005, environmental and production stresses were highlighted as major factors contributing to disease expression and their influence has become a priority for future research.
This application seeks to build on the knowledge acquired over the past 6 years by developing practical application methods for wound protection, determining the factors underlying disease expression and effects of production stresses, evaluating long-term effectiveness of control methods, determining the extent of eutypa dieback in emerging grapegrowing regions. This will improve management strategies and enhance the efficiency and sustainability of grape production for the benefit of the industry.
For more information please contact Mark Sosnowski