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In South Australian Vineyards

A. Highet¹ and T. Wicks^2
1 Current address: Southcorp Wines Pty. Ltd., P.O. Box 63, Robe, S.A. 5276.
² S.A.R.D.I., Plant Research Centre, Urrbrae, S.A. 5064.

Eutypa dieback previous known as "Dying Arm" is a lethal disease of grapevines caused by the fungus Eutypa lata. The fungus produces spores throughout the year that infect through large pruning wounds and colonise the woody tissue, eventually working down towards the roots. The fungus grows slowly in this tissue and after 3 years or more forms a canker around the infected wound, eventually killing the woody tissue. As a result arms and cordons of the vine die and yield from infected vineyards declines. Stunted shoots with small yellow and tattered leaves are produced on spurs near infected areas and are thought to be caused by a toxin produced by the fungus (Mavro et al 1988).

Eutypa symptoms are uncommon in vineyards younger than 10 years old (Carter, 1991) after which vineyard yields begin to decline. While no Australian data is available on the impact of Eutypa on vineyard yield and longevity, work in California has indicated that the disease causes yield reductions of 30 - 60% in some vineyards depending on the severity (Munkvold et al, 1994).

Apart from the early studies by Wicks (1975) there is little published data on the incidence of the disease in Australian vineyards. This present survey was undertaken to obtain data on the incidence of Eutypa in various districts and on different cultivars.

Vines at least eight years old were surveyed to determine the incidence of the problem in South Australian vineyards. This survey was carried out between late November and early December 1997 when distinctive stunted shoot symptoms are most obvious on vines infected with Eutypa.

At least 500 vines per vineyard were inspected for each cultivar and the presence or absence of stunted shoots typical to Eutypa infection were recorded for each vine. Due to time limitations with the survey, only Cabernet Sauvignon, Shiraz, Chardonnay and Riesling and in some areas Grenache were examined in the Riverland, Clare, Barossa Valley, Eden Valley, McLaren Vale, Langhorne Creek, Padthaway and Coonawarra areas. These varieties were selected for their economic value to the industry, with Grenache chosen for its susceptibility to Eutypa. The vineyards selected were those where most of the cultivars of old vines were growing in the one property. A total of 44 vineyards were surveyed which included between 3 to 8 vineyards per district.

Of the 60,000 vines surveyed, 4.7% showed stunted shoots typical of Eutypa infection. Symptoms were most prevalent in Grenache and Shiraz where 9.3% and 8.1% of vines were infected respectively. In Cabernet Sauvignon 4.2% were infected whereas less than 1% were infected in Chardonnay and Riesling.

Table 1. Incidence of Eutypa in different grape growing districts on different grapevine cultivars in South Australia – November / December 1997

Considering all the cultivars surveyed, the highest incidence occurred in the Eden Valley and Barossa Valley areas where 7.2% and 6.2% infection was detected respectively, and the lowest in Padthaway (1.6%) and Langhorne Creek (1.1%). Within varieties the highest incidence was detected in a Grenache vineyard where 46.2% of vines were infected in the Barossa Valley. Other vineyards with a high incidence were found in Eden Valley where Shiraz and Cabernet Sauvignon had 25% and 23% infection respectively.

Although the overall incidence of this disease was 4.7% it is likely to be higher than this as mild symptoms may have been difficult to detect in some of the areas inspected in December where vigorous dense shoot growth had developed and overgrown stunted shoots. Also dead or dying vines were not included in the survey as the cause of this was unknown, although much of this was likely to be caused by Eutypa infection.

Conclusion

This survey has shown that Eutypa dieback is a significant problem in mature vineyards, particularly those of the premium red cultivars Cabernet Sauvignon and Shiraz. As Eutypa is more prevalent in older vineyards this disease must be considered as one of the greatest threats to the heritage vineyards of South Australia.

Further work needs to be done to quantify the effect of the disease on vineyard production in Australia and to develop chemical and biological means of control. Particular emphasis needs to be placed in developing methods to prevent the further decline of Eutypa infected vines and the evaluation of wound protectants.

Acknowledgments

The authors wish to acknowledge the financial support from the Phylloxera Board of South Australia in commissioning this work, and the growers that gave their time and assistance with the survey.

References

Carter, M.V. (1991). The status of Eutypa lata as a pathogen. International Mycological Institute, Phytopathological Paper No. 32.

Mavro, M.C., Vaillant, V., Tey-Rulh, P., Mathieu, Y. and Fallot, J. (1988). In vitro study of the relationship between Vitis vinifera and Eutypa lata (Pers. Fr.) Tul. 1 Demonstration of toxic compounds secreted by the fungus. American J. Enol. Vitic. 39: 200-204.

Munkvold, G.P., Duthie, J.A. and Marois, J.J. (1994). Reductions in yield and vegetative growth of grapevines due to Eutypa dieback. Phytopathology. 84: 186-192.

Wicks, T. (1975). The dying arm disorder of vines in South Australia. Agricultural Record. 2: 14-20.