GWRDC and AWRI information for disease control in Australian vineyards

Australia’s 2011 vintage will be one to cause grapegrowers and winemakers both extremes of emotions. With the exception of Western Australia which has had hot and dry conditions this vintage, there have been nation-wide unseasonably wet and cool conditions.

Being involved in the wine industry in South Australia, as recently as February, everyone I spoke to was expecting a superb and bumper harvest this year. The cooler and more humid summer had resulted in huge green canopies and healthy tasty fruit. The usual problems of heatwaves and water shortages were barely a concern. 2011 was to be a year to remember. Now it will be memorable but not for the same reasons.

Disease has hit the main wine-producing states of Australia much harder than for several decades, although the impact has been by no means uniform. Some grapegrowers have lost a large proportion or even all of their fruit. Meanwhile others have coped much better, depending on their location, the grape variety in question, and the viticultural techniques applied through the season.

The main diseases of concern have been downy mildew, powdery mildew and Botrytis. All three have certainly caused problems across South Australia, with varying impacts by region. McLaren Vale, for example, was relatively disease-free until very late in the season when Botrytis kicked in, while for other regions such as Langhorne Creek and the Barossa, the Botrytis followed downy in the early part of the season affecting baby bunches and foliation, and powdery in the pre-veraison berries. The Riverland also suffered some losses due to downy prior to Botrytis. Some growers are choosing simply to dump their fruit on the ground, a heartbreaking end to what had been a promising vintage.

The good news is that many grapegrowers have followed disease control guidelines throughout the season and have sprayed to protect against disease, so a great deal of the fruit has been spared. Some growers have harvested earlier than they normally would at a lower Baumé in order to have fresh, clean fruit and to beat any diseases reaching the grapes. There is also especially good news for cabernet sauvignon lovers – people I spoke to in Barossa, McLaren Vale and Langhorne Creek all told me that the thicker skins and looser bunches of the cabernet sauvignon grapes meant that this varietal had stood up well to all disease and would be a great 2011 vintage.

Also good news is that the Grape and Wine Research and Development Corporation (GWRDC) and the Australian Wine Research Institute (AWRI) have been active in providing comprehensive and practical information for growers and winemakers in disease prevention, how to identify disease, viticultural advice to follow to minimise risks for next year, and so on. References and fact sheets are available from the GWRDC and AWRI websites. Below is a list of key references:

GWRDC Fact Sheets

GWRDC: Downy Mildew, Questions and Answers

GWRDC: Downy Mildew Monitoring (Viti-Notes) 2005

GWRDC: Powdery Mildew, Questions and Answers

GWRDC: Botrytis, Questions and Answers

GWRDC: Non-Botrytis, Questions and Answers

AWRI: Information on pests and diseases in viticulture

AWRI: Managing Botrytis infected fruit

Article by Nicola Chandler, Wine2030, University of Adelaide.

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