NSW and ACT Regional Program battles against botrytis and Brett

The Greater New South Wales and ACT wine industry proposed and implemented four major activities in 2012–13 using GWRDC Regional Program funding, with the projects set to continue next year for the benefit of 15 NSW wine regions (Riverina has a separate funding) and the ACT.

Consultant to the NSW Wine Industry Association Richard Hilder, also a joint owner of 72 hectares of vineyard in the Hunter Valley, said ‘the demonstrations and seminars planned for this year were selected in consultation with the R&D Committee within the NSW Wine Industry Association, which includes regional representatives’.

 Botrytis spraying trial

The first activity was a trial to investigate registered sprays that suppress or eliminate botrytis infection of winegrapes.

‘There was widespread botrytis infection in most regions of NSW in 2011–12 due to the drought-breaking rains that persisted up to harvest, which caught many growers off-guard’, Richard said.

A conventional spray program for botrytis was tested, along with Trichoderma mixtures, an organic spray of fungicidal potassium soap and a control treatment of no botryticides. The trial was designed by Greg Dunn and Melanie Weckert of the National Wine and Grape Industry Centre and conducted at Pyramid Hill vineyard, in the Upper Hunter.

The growing season for the 2013 vintage was relatively dry until late in the ripening period (only 43mm of rain between budburst and veraison), making conditions difficult for botrytis development. However, DPI Viticultural Officer Tony Somers assessed the trial in mid-late January and took photographs of the grape bunches in the various treatments. At that point, there were no visual symptoms of botrytis in any of the treatments. Rainfall of 118mm fell at the trial site from 27–29 January.

‘Following the rain, bunches from each treatment of the trial were taken on 30 January and stored in plastic bags in a cool section of the vineyard shed. It is too early to draw conclusions from the sampling. However, from observations, a fortnight after the samples were bagged, no botrytis was evident on the grapes protected by the organic spray of potassium soap, while botrytis in varying degrees was present in the other treatments.

The treatments in the trial were assessed by Richard Hilder and James Gardener for the incidence and severity of botrytis infection on 4 February and the grapes in the trial were picked on 7 February.

A complete report of the trial will be published before the end of June and available on the GWRDC website.

It is planned that the botrytis trial will be conducted in the same vineyard next year, and Richard said the project’s team is keen to establish a similar trial in Canberra and the Southern Highlands. He said the exciting aspect of the registered Trichoderma and organic products was their short withholding period before harvest.

Brett, tannin and acid seminar

In late January, seminars were held in Mudgee and Canberra about quantifying physiological factors in tannin and acid, and identifying sources of Brettanomyces.

About 50 winemakers attended each forum to enjoy presentations given by staff of the AWRI. The speakers, AWRI Senior Oenologist Geoff Cowey and Research Scientist Keren Bindon, presented the latest findings in tannin research, tannin structure and the related sensory affects dependent on grape ripeness and wine style. They also covered ‘Brett’ perception in different wine styles, along with monitoring, management and control strategies. Tastings of regional wines were conducted as part of the presentations, identifying tannins that reflected and supported regional character. Other tastings were held to identify Brett flavour.

The seminars will be held again in 2013–14, with the addition of information about the management of diseased grapes.

Helping Semillon survive the heat

Back in the Hunter Valley, demonstration trials relating to the use of sunburn protectant sprays to improve Semillon quality were held at McWilliams’ Lovedale vineyard and at Bimbadgen in Pokolbin.

‘The trials were assessed by Liz Riley of Vitibit and Tony Somers of the Department of Primary Industries NSW. Vineyard walks were organised at short notice, but due to the early onset of harvest, attendance was down on initial expectations’, Richard said.

A report will be written about this year’s work for distribution to local industry, and the trial will be held again in 2013–14.

Know-how for those keen to go organic

Finally, a survey is to be conducted to evaluate the application of biodynamic and organic practices to conventionally-grown vineyards in Mudgee, Hunter Valley and Canberra regions. Vineyard walks will be held in April and May this year for growers interested in learning more about the advantages about biodynamic and organic viticultural practices, but who perhaps are not concerned about certification.

For more information, contact Liz Waters, GWRDC Program Manager, liz@gwrdc.com.au