Survey of the Hunter Valley and Mudgee wine regions for the grapevine trunk disease Eutypa dieback

Mette Creaser ^A,B, Sandra Savocchia ^C, Catherine Hitch ^B and Trevor Wicks^B

^A  Cooperative Research Centre for Viticulture, PO Box 154, Glen Osmond SA 5064

^B  South Australian Research and Development Institute, GPO Box 397, Adelaide SA 5001

^C National Wine and Grape Industry Centre, Charles Sturt University, School of Wine and Food Sciences, Locked Bag 588, Wagga Wagga, NSW 2678.

Introduction

Eutypa dieback, caused by the fungus Eutypa lata, is an insidious disease that contributes to the decline of vineyards by reducing growth and yield and eventually killing vines.  Highet and Wicks (1998) showed that the disease is widespread in South Australia, occurring in all grape growing areas and on all varieties.   However, despite the high occurrence of Eutypa dieback in South Australia, a recent review of grapevine samples received for diagnosis in NSW found no record of E. lata isolation from grapevines from the Hunter or Mudgee wine regions (Tony Somers, personal communication).  It has been suggested that other pathogens such as Botryosphaeria species, may attack grapevines in these regions rather than E. lata. 

In a survey of Semillon vines in the Hunter Valley, Botryosphaeria obtusa was commonly isolated from vines with dead spurs and cordons (Castillo-Pando et al., 2001).  However, symptoms of Eutypa dieback are rarely observed in Semillon suggesting that a more extensive investigation of the disease was necessary, particularly amongst more susceptible varieties such as Shiraz and Cabernet Sauvignon in the region. 

Vineyards of different ages and varieties in the Hunter Valley and Mudgee wine regions were surveyed for Eutypa dieback in early November 2002.  Vines in 20 vineyards were inspected for foliar and wood symptoms of the disease.  Wood samples were taken from five vines in each vineyard and tested for the presence or absence of Eutypa lata and other fungi. 

Results and Discussion

Many vines were found with dead spurs or cordons (Figure 1a-b), which when cut in cross-section showed a wedge of discoloured tissue (Figure 2a-c) similar to the wood symptoms observed in E. lata infected vines (Figure 3a).  However, the characteristic foliar symptoms of Eutypa dieback (Figure 3b) were not observed in any of the vineyards inspected (Table 1).  Furthermore, E. lata was not isolated from any of the wood samples taken from the two regions.  However, some fungi were recovered and preliminary identification suggests that a species of Botryosphaeria may be associated with dead wood.  Further testing is required to confirm their identification. 

Table 1.  The variety and age of vineyards surveyed.

In the USA, there is a climatic divide between the occurrence of Eutypa dieback (caused by E. lata) and Botryosphaeria dieback or Bot canker (caused by a species of Botryosphaeria) (Leavitt, 2003).  A similar climatic divide may separate the occurrence of these two trunk diseases in Australia.  The Hunter Valley experiences a warm to hot, sub-tropical climate whereas South Australia experiences a Mediterranean climate with hot dry summers and wet winters.

Further work is now required to determine:

• the species of Botryosphaeria responsible for the symptoms observed in the Hunter and Mudgee regions
• the occurrence and impact of Botryosphaeria dieback in Australia
• whether there is a climatic divide between the occurrence of Eutypa dieback and Botryosphaeria dieback
• the epidemiology of the disease. 

Conclusions

• Foliar symptoms of Eutypa dieback were not observed in any of the 20 vineyards surveyed in the Hunter Valley or Mudgee regions.
• Wood symptoms similar to those found in Eutypa dieback affected vines were observed in vines from the Hunter Valley and Mudgee.
• Eutypa lata, the causal agent of Eutypa dieback was not isolated from any the vines sampled from these regions.
• Diagnosis of E. lata infection cannot be made using wood symptoms alone, but must be accompanied by observation of foliar symptoms or isolation of the fungus from wood.
• Preliminary identification suggests that other fungi, such as those belonging to the Botryosphaeria genus may be associated with dieback in these regions. 

References

Castillo-Pando M., Somers A., Green C.D., Priest M., and Sriskanthades D. (2001).  Fungi associated with dieback of Semillon grapevines in the Hunter Valley of New South Wales.  Australasian Plant Pathology 30:59-63.

Highet A. and Wicks T. (1998) The incidence of Eutypa dieback in South Australian vineyards.  The Australian Grapegrower and Winemaker Annual Technical Issue 1998.

Leavitt G. M. (2003) The occurrence, distribution and control of Botryodiplodia theobromae on Vitis vinifera in California, Arizona and north Mexico. In proceedings of the 3^rd International Workshop on Grapevine Trunk Diseases, Christchurch, 1-2 February.

Acknowledgements

We thank the many growers and vineyard managers who kindly allowed us access to their vineyards and to Tony Somers and Clarrie Beckingham of NSW Agriculture for their invaluable assistance. 

This project is being conducted by the CRC for Viticulture and is supported by Australia’s grapegrowers and winemakers through their investment body the Grape and Wine Research and Development Corporation, with matching funds from the Federal Government through the Commonwealth Cooperative Research Centre program.

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