The Australian Wine Research Institute

19 March 2024

As reported in the AWRI eBulletin on 22 February, a number of vineyards across Australia have reported crown gall-like symptoms in vines in recent months. An industry response group has been convened to coordinate the response to this issue. The group includes representatives from AWRI, Australian Grape & Wine, Wine Australia, VINA, SAVIA, State Government Departments, Vinehealth Australia and diagnostic laboratories, and is developing eight project areas where work is needed to better understand and respond to this situation.

These project areas are:

• Data and information collection and analysis (led by AWRI)
• Communication to industry (led by AWRI)
• Pathogen identification (led by the University of Adelaide)
• Diagnostic protocols (led by the University of Adelaide)
• Identification of source (led by VINA, with support from AWRI)
• Nursery disinfestation procedures (lead organisation to be confirmed)
• Farm-gate hygiene procedures (lead organisation to be confirmed)
• Biological control (lead organisation to be confirmed)

Pathogen identification and diagnostic protocols

Although Agrobacterium has been implicated, the identity of the disease-causing agent is currently unclear. It may be an endemic pathogen, a new pathogen or a combination of pathogens across different locations. To address this, Dr Sharon Harvey from Wine Australia recently convened a meeting of representatives from a number of diagnostic laboratories and research organisations to review the progress made in identifying the causal agent and to coordinate a response to address any existing gaps. To support these goals, Assoc. Prof. Iain Searle from the University of Adelaide is leading the development of a project proposal for submission to Wine Australia. This project will aim to identify the pathogen responsible for the outbreak and develop essential diagnostic tools. It will be conducted in collaboration with organisations such as the AWRI, DPI NSW, QLD DAF, Affinity Labs, Crop Health Services of Agriculture Victoria, as well as DPIRD (WA) and Biosecurity Tasmania.

Diagnostic testing currently only has the capacity to identify potential pathogens. In light of this, growers are advised to hold off on submitting samples for testing until new diagnostic tools have been developed. This precautionary approach will ensure that testing provides growers with the most reliable information for decision-making.

Identification of cause of symptoms

The industry response group is actively collaborating with affected growers, the propagation sector and State Departments to thoroughly investigate potential sources and causes of the disease outbreak. Present findings suggest that the crown gall-like symptoms are isolated to a limited number of vineyards in Queensland, NSW and Victoria. At this stage, it remains unclear whether the disease outbreak originated from infected planting material, environmental influences, cultural practices, or a combination of these and/or unknown factors.

As part of these efforts, the propagation sector has already been conducting traceback activities to source blocks, testing grapevine material, and reaching out to customers. In addition, the AWRI is maintaining a central database of symptom detection to aid in traceback activities, track diagnostic test results, understand disease progression and assist growers.

Once the pathogen is accurately identified and its origin more clearly understood, the industry response team will work to develop measures to limit the spread of the disease. The objective is to have these enacted before the onset of the propagation season in June 2024.

New fact sheet

An AWRI fact sheet on crown gall is now available. This fact sheet summarises the current knowledge on crown gall disease, classification of the associated Agrobacterium and Allorhizobium bacteria, symptoms, control measures and the current status of diagnostics.

Grower information form

A form for growers to record cases of gall-like symptoms is also now live, to support the collection of a comprehensive data set describing the extent of this problem across Australia. All growers who have observed gall-like symptoms are encouraged to report them using this form. Information provided may be shared with members of the industry working group but will not be revealed publicly or shared outside this group.

A reminder of what to do if you observe gall-like symptoms:

• Photograph and document the location of affected vines.
• Log the symptoms using the grower information form.
• For new vine plantings, contact your nursery supplier and the Vine Industry Nursery Association (VINA) on 0429 772 221 or steve@armnursery.com.au.
• Contact the AWRI helpdesk on 08 8313 6600 or helpdesk@awri.com.au for advice on next steps.

For more information about crown gall, the industry response group or any other technical viticulture or winemaking question, please contact the AWRI helpdesk on 08 8313 6600 or helpdesk@awri.com.au.

Acknowledgments

The AWRI’s eBulletin is supported by Wine Australia, with levies from Australia’s grapegrowers and winemakers and matching funds from the Australian Government. The AWRI is a member of the Wine Innovation Cluster in Adelaide, South Australia. Members of the crown gall industry response group are thanked for their contributions.

 

22 February 2024

The AWRI helpdesk has received reports of crown gall-like symptoms affecting young vines in a number of regions in Australia.

Preliminary analysis conducted by laboratories in NSW and Victoria has suggested the presence of Agrobacterium species from the biovar 1 group in the galls. This finding is unexpected given that the predominant causal agent for crown gall disease historically in Australian vineyards has been Allorhizobium vitis (previously referred to as Agrobacterium vitis), which belongs to the biovar 3 group. While Agrobacterium species from the biovar 1 group have not previously been associated with crown gall disease in Australian vineyards, they are known to induce similar symptoms in other plant species, including pome fruit, stone fruit and nut trees.

Agrobacterium and Allorhizobium species are commonly found in soils and water worldwide, where they typically lead saprophytic lives, surviving independently of a host. However, when they infect plants, they can either be non-pathogenic or act as pathogens, causing diseases. Pathogenicity is linked to virulence genes on a tumour-inducing plasmid (Ti plasmid). Among the known strains of Agrobacterium from the biovar 1 group, some exhibit pathogenicity towards plants while others do not. Testing is currently underway on vines displaying the crown gall-like symptoms, to determine the specific strain(s) present. Once identified, further investigation will be necessary to demonstrate whether or not these strains are pathogenic towards grapevines.

Symptoms
The symptoms that have been reported are gall formation at wound sites, stunted growth, peeling and cracking of bark, as well as a gradual decline in vine vigour and vine loss due to girdling as the disease progresses. Young vines are particularly vulnerable as galls can impede water and nutrient flow throughout the vine. Frost injury causing cracking of the bark has led to small tumours forming in a line along the cracking wound. Symptoms of crown gall can also be mistaken for those of vine strangulation around the graft union and root knot nematodes.

Response
In response to this issue, a group of representatives from industry bodies including the AWRI, Wine Australia and Vinehealth Australia, diagnostic laboratories, the propagation sector, research organisations, state biosecurity bodies and growers are working together. This group aims to identify the causal organism(s) of crown gall-like symptoms in affected vineyards, identify the source of infection, and establish best practice management guidelines for infected vineyards.

Efforts are also currently underway to align and enhance diagnostic techniques for identifying Agrobacterium and Allorhizobium species across multiple Australian laboratories.

Vineyard hygiene
There are currently no effective and practical methods available for completely eradicating crown gall once the bacteria are established in a vineyard, primarily due to their ability to persist in the soil for extended periods. Until more information becomes available, growers are strongly advised to adhere to best-practice farm gate hygiene. Given the potential spread of Agrobacterium and Allorhizobium bacteria through contaminated soil, water and equipment, strict hygiene measures are imperative to minimise the risk of spread. These measures include segregating vineyard activities between clean and diseased blocks, regularly disinfecting tools and equipment in contact with soil or vines, preventing the transfer of soil or plant debris between blocks, and ensuring contaminated water does not flow into clean areas or water storage facilities.

Vinehealth Australia provides a list of ‘Top farm-gate hygiene activities’ and protocols outlining procedures for disinfecting footwear or small tools, and harvester cleaning. While these are primarily aimed at minimising the introduction of phylloxera, it is important to note that for farm gate hygiene disinfestation procedures to be effective, they must address the target pest, disease or pathogen. The latest recommendation to target crown gall is to use undiluted methylated spirits (95% ethanol) to disinfest footwear and small hand tools. Growers using ethanol in footbaths are advised to follow a two-step process to ensure footwear is first cleaned of all soil and plant material, prior to submersion in the ethanol for 60 seconds, with no water rinse thereafter. The efficacy of the ethanol will be prolonged by covering the footbath securely during daylight hours when not in use to prevent degradation, and replacing the ethanol at least daily or more frequently if it becomes soiled. This disinfestation procedure is also effective against phylloxera. Note that caution is advised because 95% ethanol is highly flammable.

What to do if you observe gall-like symptoms:

• Photograph and document the location of affected vines.
• For new vine plantings, contact your nursery supplier and the Vine Industry Nursery Association (VINA) on 0429 772 221 or steve@armnursery.com.au.

Contact the AWRI helpdesk on 08 8313 6600 or helpdesk@awri.com.au for advice on options for testing and identification.

Acknowledgments

The AWRI’s eBulletin is supported by Wine Australia, with levies from Australia’s grapegrowers and winemakers and matching funds from the Australian Government. The AWRI is a member of the Wine Innovation Cluster in Adelaide, South Australia.

Suzanne McLoughlin from Vinehealth Australia is thanked for her contributions to this eBulletin

11 January 2024

During the Christmas and New Year period, extensive rainfall, and hail in some regions, affected several grapegrowing regions in Australia. These conditions were conducive to the development of fungal diseases such as downy mildew, powdery mildew and Botrytis in grapevines. Tools and resources available to grapegrowers and winemakers to manage disease assessments are detailed within this Ask the AWRI article on assessing grapes for disease.

Looking ahead, the forecast for rainfall from January to March suggests a likelihood of above-median rainfall in the south-east, while the north and west of Australia may experience below-median rainfall. Immediate action is crucial to mitigate the risk of significant crop losses from fungal disease. This eBulletin outlines strategies to reduce both the risk and severity of fungal infections during periods of heightened disease pressure.

General tips for best-practice disease control
In high-vigour blocks, consider shoot thinning, trimming, leaf removal and bunch thinning to enhance canopy openness, allowing better light and air penetration. This practice not only accelerates canopy drying post-rainfall but also facilitates improved spray penetration and chemical deposition.

Vineyard floor management, such as keeping mid-row cover crops low to support airflow and canopy drying, is another strategy to put in place. In addition, if a neighbouring vineyard has opted to ‘rest’ their block, a strategic approach could involve treating a few boundary rows to mitigate disease pressure stemming from those vines.

Chemical options for powdery mildew, downy mildew and Botrytis control are listed in the ‘Dog book’. These recommendations are for fruit destined for export wine. Agrochemicals applied to fruit destined for the domestic wine market have shorter withholding periods and these are found on the label. Ensure you consult with your grape purchaser or the AWRI if you are considering chemical options that do not follow the ‘Dog book’ recommendations for export wine.

Effective spray coverage is critical for successful disease control. Test your spray coverage using water sensitive papers or a kaolin-based clay sunscreen. Once your equipment is set up well, check that you’re applying the correct chemical rate to avoid underdosing. Operating a spray unit in the same direction for every spray application runs the risk of missing the same hard-to-reach parts of the canopy each time, potentially creating a disease hotspot. Spraying in a different pattern so that the opposite direction is travelled up the row has potential to improve overall coverage.

Ask your supplier about available products and their features, particularly regarding rainfastness (the ability of a product to remain on the target after rain or heavy dew). Different products perform differently during prolonged wet periods. Also, check the compatibility of these products with adjuvants designed to improve rainfastness. The relationship between spray coverage and retention is a function of agrochemical mixes and rates, spray application volumes, canopy type and the target canopy tissues (leaves, wood or bunches of fruit) (Gaskin et al. 2002). Choosing the right product for the current conditions is crucial, as it might differ from what’s suitable during drier years.

In situations where resources and time are constrained, prioritisation becomes crucial. Identify your most profitable blocks and concentrate on securing a healthy crop from those areas. Monitoring is important and instructions on how to recognise powdery mildew, downy mildew and Botrytis are provided in the resources linked below.

Downy mildew
Applying preventative sprays prior to an infection event is crucial to controlling downy mildew in wet years. Fungicides are in high demand during wet seasons, so keeping a chemical supply available is wise. Most registered products for downy mildew act as protectants. Avoid using these on an active infection to prevent resistance, which could lead to losing the efficacy of the product in the future. If you have had a downy mildew infection event and are using a metalaxyl (group 4) for curative control, then a second group 4 spray on a 7–10-day interval is required.

While the AWRI website provides information on phosphorous acid use, it is crucial to communicate with your winery or grape purchaser before applying this product. Some export markets maintain low tolerance for phosphorus acid residues, necessitating careful consideration before its use.

Additional downy mildew resources

• Downy mildew update (AWRI eBulletin 19 November 2021)
• AWRI’s resources on downy mildew
• Wine Australia’s resources on downy mildew
• WA Department of Primary Industries and Regional Development’s information on downy mildew
• Control strategies for downy mildew and Botrytis(AWRI webinar 9 November 2018)

Powdery mildew
The optimal strategy for combatting powdery mildew involves consistent application of protective chemicals early in the season to protect all growth from this disease. Preventing its establishment in the initial stages is pivotal for minimising the disease load later on. Unfortunately, this season posed challenges, hindering the application of early sprays in numerous vineyards or diluting those already applied due to heavy rain periods. These conditions have heightened the risk of powdery outbreaks. In such scenarios, taking preventive action to avoid a widespread powdery disease epidemic becomes absolutely essential.

Elemental sulfur is a multi-site fungicide which is not susceptible to resistance and has some curative activity. To gain control of an existing infection using sulfur, good spray coverage is essential. An active powdery mildew infection may repel water, so ensuring adequate spray coverage is crucial. Consider using an adjuvant to enhance coverage on challenging-to-wet surfaces. Some sulfur products include built-in adjuvants, enhancing their spread on plant surfaces. For other sulfur products, consult your chemical supplier to determine if an adjuvant is needed to improve spread.

Some production zones across Australia are experiencing earlier ripening conditions compared to previous seasons. Ensure applications of sulfur adhere to the pre-harvest cut-off timeframes if used for late-season powdery mildew management.

Some single-site chemicals exhibit curative activity against powdery mildew but using them on active infections is not advised due to the heightened risk of resistance development. CropLife Australia recommends applying single-site fungicides preventatively before colony formation for effective powdery mildew control.

Additional powdery mildew resources

• AWRI’s resources on powdery mildew
• Wine Australia’s resources on powdery mildew

Botrytis bunch rot
Late-season Botrytis expression can create significant challenges for growers formulating strategies for variable site locations and varietal mixes. This requires a sound understanding of the pathogen and how it interacts with various late-season fungicide modes of actions. Many biological fungicides provide optimal protection when used prior to visual expression of disease symptoms. Disease control may be less than optimal when products are employed reactively for curative purposes. All spray options for late-season Botrytis management require good coverage of bunches and berries. Strategic canopy and fruit zone management not only enhance spray droplet coverage but also promote better airflow around the bunch zone.

When Botrytis is already evident in tightly clustered bunches, causing juice leakage from the berries, spraying might not be effective. In such cases, hand removal of affected bunches or selective harvesting may be an option. Controlling for downy and powdery will also help manage Botrytis.

Research from New Zealand suggests that maintaining 70-90% bunch exposure by selectively removing leaves from late flowering to pre-harvest significantly reduces Botrytis risk (Andrew and Lupton 2013). However, caution is necessary with leaf plucking to avoid sunburn, especially in hot regions, if excessive leaf removal occurs later in summer.

Botrytis can cause problems during winemaking as it produces an oxidative enzyme called laccase, which, in the presence of oxygen, can cause oxidative spoilage and rapid browning of must. Laccase activity is the main marker for Botrytis infection and can be detected using enzymatic test kits so it is advised to have these ordered or in stock. Botrytis can produce polysaccharides that cause clarification problems in juice and filtration issues in wine. It can also impart mouldy flavours, and together with bacteria, increase the chance of elevated levels of acetic and lactic acid. The AWRI fact sheet Managing Botrytis-infected fruit, must and wine details winemaking strategies for processing both white and red grapes affected by Botrytis.

Additional Botrytis resources

• AWRI’s resources on Botrytis
• Wine Australia’s resources on Botrytis
• Control strategies for downy mildew and Botrytis(AWRI webinar 9 November 2018)
• Botrytis information pack

Don’t forget to look after yourself and your mates
When conditions are challenging, it can increase stress and add to existing pressures. Check on your mates and if you are in a difficult spot, it is important to talk about it. There is help available in your local community and from these organisations: Beyond Blue, Lifeline, Headspace, R U OK?, Black Dog Institute.

Additional resources on fungal diseases and dealing with wet conditions

• Gaskin, R., Manktelow, D., Elliott, G. 2002. New adjuvant technology for pesticide use on wine grapes. NZ Plant Prot.55: 154–158.

• Tips on assessing fruit condition in a season with high disease pressure (AWRI eBulletin 22 February 2023)
• Non-botrytis bunch rots: Q and A  (Wine Australia fact sheet)

• Managing disease in wet conditions (AWRI eBulletin 12 November 2021)
• Managing waterlogged vineyards (AWRI fact sheet)
• Flooded vineyard case studies (Wine Australia fact sheet)

Acknowledgements
This eBulletin is supported by Wine Australia with levies from Australia’s grapegrowers and winemakers and matching funding from the Australian Government. Liz Riley (Vitibit), Warren Birchmore, Philip Deverell (Pernod Ricard Winemakers) and Scott Paton (Nutrien Ag Solutions) are thanked for their contributions.

For more information or assistance, please contact the AWRI helpdesk on 08 8313 6600 or helpdesk@awri.com.au.

 

18 November 2023

The AWRI will be closed over the Christmas/New Year period from midday on Friday, 22 December and will re-open at 8:30am on Tuesday, 2 January 2024. Most AWRI staff will be on leave until Monday, 8 January 2024. Affinity Labs  Affinity Labs will be closed from midday on Friday, 22 December and will re-open at 9:00am on Monday, 8 January 2024. Helpdesk support  AWRI helpdesk staff will be on leave from Friday, 22 December 2023 to Monday, 8 January 2024. Telephone support will be available for urgent or emergency assistance during this period. If you require urgent assistance, please contact: Geoff Cowey on 0448 736 145 for winemaking issues Mardi Longbottom on 0431 830 922 for viticulture issues. For less urgent queries, please email helpdesk@awri.com.au and the team will get back to you after 8 January 2024. Smoke testing and support   If there is major smoke event over the Christmas/New Year period, AWRI and Affinity Labs staff will return to work to ensure testing services and technical support are available. Sustainable Winegrowing Australia support   For any enquiries about Sustainable Winegrowing Australia, please email helpdesk@awri.com.au and the team will get back to you after 8 January 2024. Library  The John Fornachon Memorial Library will be closed from midday on Friday, 22 December and will re-open at 9:00am on Monday, 15 January 2024. Access to the library’s online database will continue to be available 24 hours a day, 7 days a week via the AWRI website.

An election for a position on the AWRI Board was recently held in the medium Wine Grapes Levy payer category (2,001 – 50,000 tonnes). Nominations were also called for candidates to contest an election in the small Wine Grape Levy payer category (up to 2,000 tonnes). Only one nomination was received in that category and therefore the candidate was automatically elected.

The AWRI is pleased to announce that Brett McClen (Brown Family Wine Group, Vic.) was re-elected in the medium category and Corrina Wright (Oliver’s Taranga and Oliver & Press Winemakers, SA) was re-elected in the small category.

Brett McClen is Head of Viticulture and Sustainability for Brown Family Wine Group. In this role he oversees all the company’s grapegrowing across a total of 830 ha of vineyards located across the Murray Valley, King Valley, Heathcote and Tasmania. He is also responsible for the company’s sustainability agenda as well as the Infrastructure and Reliability portfolio. Brett has an Honours degree in Agriculture Science and a Master’s degree in Business Administration. He has served two terms as a Director of the Australian Society of Viticulture and Oenology and one term as a Director of the AWRI.

Corrina Wright is winemaker and director at the helm of sixth generation family business, Oliver’s Taranga, plus new contract processing facility Oliver & Press Winemakers in McLaren Vale. She was awarded the ASVO Winemaker of the Year 2019 for her contribution to the wine community. She graduated from the prestigious Len Evans Tutorial in 2005 and continues to judge and chair numerous wine shows around Australia. Her commitment to the wine industry in Australia was rewarded with a position on the inaugural ‘Future Leaders – Succession for the Australian Wine Industry’ program in 2006. Passionate about her home, her vocation and local community she has also served on the boards of the McLaren Vale Grape, Wine & Tourism Association, the Australian Society of Viticulture & Oenology, Family Business Australia, and the Winemakers’ Federation of Australia. She is currently part of the Australian Women in Wine Awards advisory board, the Diversity, Equality & Inclusion committee for Australian Grape & Wine and has served one term as a Director of the AWRI.

Both Directors will commence their new elected terms on 1 January 2024. The term of outgoing Board member Liz Riley concluded on 31 October 2023 following 12 years on the AWRI Board, and the term of Nigel Sneyd will conclude on 31 December 2023. The AWRI thanks Liz and Nigel for their significant contributions over their time on the AWRI Board.