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Cross-section of a Eutypa-infected grapevine trunk with wedge-shaped staining of dead wood. Photo: SARDI.

WINEGRAPE growers are closer to protecting high-value vines against the trunk disease Eutypa with a registered fungicide that can be applied to pruning wounds with a vineyard sprayer.

A three-year research project on managing Eutypa dieback  has identified effective new pruning-wound treatments including the grapevine fungicide Emblem (fluazinam) at rates registered for protectant pre-budburst control of phomopsis.

The collaborative research was conducted by the South Australian Research and Development Institute (SARDI), the University of Adelaide and the Grape and Wine Research and Development Corporation (GWRDC).

Based on this research, Crop Care has made a submission to the Australian Pesticide and Veterinary Medicine Authority (APVMA) to register Emblem for Eutypa control.

SARDI science leader Dr Mark Sosnowski said having registered Eutypa fungicides that can be applied with a sprayer would be an important step in the bid to save Australia’s premium quality vines from devastation by trunk disease.

He said trunk disease threatened the long-term sustainability of the Australian wine industry and the incidence was steadily increasing.

“I am yet to find a wine region in Australia that is not affected by eutypa and/or botryosphaeria dieback – the two most important trunk diseases in Australia and in most other grape-growing countries around the world.”

Dr Sosnowski said a GWRDC-commissioned economic study ranked trunk disease as the fourth most important grapevine disease in terms of economic impact – behind powdery, downy and botryitis.

“There are many effective registered treatments for the first three, but very little registered for trunk disease, and nothing that can be applied with a commercial sprayer,” he said.

“This highlights the significance of having products such as Emblem registered for use as pruning wound protectants.

“If we are to sustain our premium vineyards across Australia, post-pruning sprays will need to become common place, and this can only be achieved with effective fungicides that are registered for this purpose.

“Currently the only method of controlling Eutypa dieback once it is established in vines is by removal of all infected wood tissue. A more cost-effective method of control is to prevent disease entry into the vine by protecting wounds.”

The economic impact of Eutypa has not recently been calculated however in 1999, Dr Trevor Wicks (formerly of SARDI) calculated the yield loss in Shiraz was up to 1500 kg/ha when 47 per cent of vines were symptomatic.

“It is common these days to find vineyards with 100% symptomatic vines in older regions. Eutypa dieback is recognised as a significant problem in most cool-climate growing regions of southern Australia where it threatens the sustainability of many vineyards,” Dr Sosnowski said.

The fungus infects vines through pruning wounds, and colonises wood tissue causing dieback of cordons, stunting of green shoots, leaf distortion, poor fruit set, uneven berry ripening and eventually death of vines if not controlled.

Eutypa dieback can be controlled by protecting wounds from infection by the fungus; by physically removing infected wood and retraining watershoots from below the infection; by avoiding pruning in wet conditions; and with good vineyard sanitation.

As well as potential treatments, the recent research also looked at the use of commercial sprayers to effectively apply treatments to pruning wounds.

“High-volume recycle sprayers and a home-engineered cordon sprayer maximised spray coverage on the wounds, and provided control equivalent to treatments applied by paintbrush,” Dr Sosnowski added.

“Spray application of an effective fungicide would provide an economically viable Eutypa-control alternative to hand application.”

Emblem, containing fluazinam, is a non-systemic protectant with multi-site activity and is a group 29 fungicide, regarded as being low risk for developing fungicide resistance.

Emblem is already registered for use in Australian vineyards for the control of phomopsis as a dormancy application, and has good residual and rainfast properties.

Last year the re-entry period for Emblem was reduced, allowing workers to return to the vineyard for pruning, training vines and disease scouting as soon as the spray has dried.

This change applies only to Emblem fungicide, and not to other registered fluazinam products.

If this year’s APVMA submission is successful, Emblem would be the only fungicide with label registration for Eutypa control that can be applied with a vineyard sprayer.

Dr Sosnowski said fluazinam (Emblem) was also shown to control botryosphaeria dieback in preliminary research, but more data was required before registration could be considered for that disease.

“That research is currently underway as part of a continuing project with GWRDC and many research and industry partners to fill gaps in knowledge about managing trunk disease.”

Australia continues to lead research into the management of grapevine trunk diseases, with limited research currently occurring elsewhere in the world.

Dr Sosnowski said it was therefore important to continue with the research for the long-term viability of the Australian wine industry.

Australia will host the 9th International Workshop on Grapevine Trunk Diseases at the National Wine Centre, Adelaide in November this year.

CONTACTS:

Dr Mark Sosnowski

Science Leader, Plant Health & Biosecurity, SARDI

Phone: 61  8 8303 9489

Email: mark.sosnowski@sa.gov.au

 

Doug Wilson

R&D Projects Coordinator, Nufarm Australia

Phone: 61 3 9282 1427

Email: doug.wilson@au.nufarm.com

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