Growers respond to trunk disease threat

An industry ‘evolution’ is occurring as growers learn to better protect their vineyards against grapevine trunk diseases Eutypa dieback and Botryosphaeria dieback.

National Wine and Grape Industry Centre Research Associate Wayne Pitt said as more research and work is undertaken and presented to the industry, growers have come to accept the real threat that trunk disease poses to yield and vineyard longevity.

‘There is a bit of an evolution occurring around this issue, and I suspect now the majority of growers are aware of these diseases and have the capacity to identify some of the common symptoms’, Wayne said.

‘The industry is very responsive and in a lot of ways quite proactive, but until recently many growers may not have been aware of the problem and, as a result, have not had a great deal of information about the pathogens that cause trunk diseases.’

Though still learning about the lifestyles of these fungi, Wayne said they now understood a lot more about the pathogen and its epidemiology.

‘By understanding the pathogen we are much better positioned to develop strategies to prevent and manage the diseases they cause.’

For example, the NWGIC team now advocates preventative strategies such as:

  • Avoiding pruning in the rain, and up to 36 hours after rain (fungal spores are released and remain active during this time), and
  • Limiting the size and number of wounds and treating all larger wounds with a wound sealant.

‘But we also realise that there are few options for growers with regard to wound treatments, and currently only two products, Greenseal and Vinevax, are registered for pruning wound protection’, he said.

‘Hence, we are now establishing additional field trials to further assess efficacy of promising wound treatments, and we are also working to identify critical times for usage that provide the best protection of pruning wounds.’

Additionally, Wayne said, they now suggest growers prune early in the season when spore numbers are low, or later in the season, when wounds heal more quickly with the onset of higher temperatures.

‘However, at present the optimum time for pruning that presents the least risk of infection to pruning wounds is unknown, and so we are also establishing trials to look at how long wounds remain susceptible to infection after pruning when conducted at different times throughout the traditional pruning period.’

NWGIC has held numerous grower workshops throughout NSW and Victoria, and more are scheduled for NSW, South Australia, Queensland and Tasmania later in the year as part of the GWRDC Regional Program.

‘The workshops provide growers with the most up-to-date information on trunk diseases and their management, but also opportunities for growers to interact directly with researchers, and to discuss these issues and their experiences with each other’, Wayne said.

From 2013–16, researchers at NWGIC and the South Australian Research & Development Institute will collaborate on a project, funded by GWRDC and industry partners, to help provide growers with appropriate pruning practices to minimise trunk disease infection and identify the critical time for fungicide application for the protection of pruning wounds.

Additional trials that will look at remedial surgery as a management strategy for Botryosphaeria dieback will be set up throughout the Riverina and Hunter Valley as part of the project.

For more information contact Elise Heyes, GWRDC Program Manager, elise@gwrdc.com.au

Image: Cabernet Sauvignon vines being monitored as part of the current trunk disease research in the NWGIC vineyard in Wagga Wagga.

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