Murray Valley takes a new approach to fighting powdery mildew

A new focus on powdery mildew and an ongoing study of the potential for oxygen injection into irrigation water to improve vine growth in marginal soils are two of the main priorities for Murray Valley Winegrowers Inc (MVWI) in the year ahead.

Research suggests there is significant opportunity for improved powdery mildew control if growers use fungicides more strategically, which may also allow them to reduce the number of sprays. A small-scale demonstration trial funded by Wine Australia aims to test that in local conditions.

Small demonstration blocks were established in seven vineyards in September and will be closely monitored over the next two years.

There is every reason for optimism. Downy mildew used to be considered a greater cost to the sector than powdery mildew until a concerted campaign to improve spraying practices reduced its impact significantly.

‘Powdery mildew has been identified as having the greatest economic impact of any of the pests and diseases currently affecting Australian wine grape vineyards (after birds) and the cost to the sector has been estimated at more than $70 million annually’, said the MVWI’s new Industry Development Officer, Julian Connellan.

‘Wineries in the Murray-Darling and Swan Hill wine region have indicated that it remains an issue in varieties such as Chardonnay and Verdelho, with the incidence of the disease in fruit varying from year to year.’

It is not uncommon for growers in the Murray Valley and other inland wine regions to spray a dozen times a season or more. However, a recent study in the Riverland has concluded that as few as four sprays may be adequate, allowing for environmentally cleaner and cheaper control.

‘As in the case of downy mildew, it is believed that this can be achieved by deploying an improved understanding of the epidemiology of powdery mildew in Australian vineyards and a strategically refined spray timing in relation to infection potential’, Mr Connellan said.

‘This, along with ensuring spray machinery, is calibrated and set up correctly for maximum performance, has potential to maximise the effectiveness of spray programs, reduce input costs and enhance the profitability and sustainability of wine growers in the Murray Valley.’

A project team is working with each participating grape grower to develop and closely document a new spraying regime for their demonstration block, while standard practices continue elsewhere in the vineyard. Towards the end of the first season a field day will be held at selected sites to showcase the outcomes.

The ongoing project to inject oxygen into irrigation water, which is a collaboration between MVWI and the NSW DPI funded by Wine Australia, is hoping to provide better growing conditions for vines in heavy clay soils.

The continual watering needed in the Murray Valley during summer tends to make already marginal soils more anaerobic, and researchers are trying to determine whether adding oxygen to irrigation water can provide an improved environment for vine growth, hopefully resulting in improved yields and fruit quality.

The work has received a boost this year with the arrival of new oxygen injection equipment in September that was borrowed from Central Queensland University. This equipment has been used with success in trials with other crop types in Queensland. The trial site at Curlwaa, in south-western NSW, has been slightly modified to suit the new equipment.

MVWI has provided six probes that allow for continuous soil moisture monitoring across the site and there are also sensors buried across the vineyard to continuously monitor soil oxygen levels.