Best practice management of grapevine viruses in Australia
Abstract
The symptoms of virus infection are increasingly recognised in Australian vineyards. Leafroll (caused by GLRaV-1 and GLRaV-3) and Shiraz Disease (caused by GVA) are rising in incidence and are perceived as having economic impact in many grape growing regions. The negative effects include reduced vine vigour as well as reduced grape quality and yield, providing a challenge for growers and wine companies.
To address this, a research team from The New Zealand Institute for Plant and Food Research Inc, led by Dr Vaughn Bell, developed a set of management strategies for grapevine viruses in Australian viticulture. It offers a multi-faceted approach to virus management, both in established vineyards and new vineyard plantings, much of it based on the New Zealand experience in responding to Grapevine leafroll disease.
The guide contains the latest research information and can be used by grapegrowers and viticulturists to identify, monitor and manage viruses and their insect vectors in vineyards. It offers users an opportunity to restrict the spread of grapevine viruses within and between vineyards. In addition, the team identified key knowledge gaps around grapevine viruses and their impact and management in Australia. These insights will help guide future research investment.
Summary
Grapevine viruses pose a significant risk to the productivity, quality and economic sustainability of Australian vineyards. There are 12 grapevine viruses known to be present in Australia, with approximately another 80 identified globally. The notable viruses of economic importance to grape-growing in Australia are Grapevine leafroll-associated virus 1 and 3 (GLRaV-1 and -3), which causes Grapevine leafroll disease, and Grapevine virus A (GVA), which causes Shiraz disease. The viruses negatively impact both grapevine productivity and grape quality. Minimising the impact and spread of endemic viruses, and preventing the establishment of new exotic viruses, is a priority to protect Australian wine.
Grapevine viruses appear to be spread readily within and between vineyards by insect vectors, most notably mealybugs and soft scale insects, and through the use of infected propagation material.
Management of viruses is challenging, and growers require standard protocols for virus and vector control that are tried and tested. To address these challenges, we issued a Request for Proposal in August 2020 to deliver a how-to guide for virus management for the Australian wine sector. A research team from The New Zealand Institute for Plant and Food Research Inc, led by Dr Vaughn Bell, delivered the project. The team includes scientists and personnel closely connected to New Zealand Winegrowers and with many years of research and practical experience of grapevine virus management in New Zealand.
The guide contains the latest research information and focuses on preventative measures and early intervention to reduce and contain virus spread. It details an integrated (multi-tactic), whole-of-industry response, which includes:
- Detection of virus infection in grapevines
- Identification and removal of diseased grapevines
- Monitoring and managing insect vectors of grapevine viruses
- Using vines certified as virus-free when planting.
Underpinning an integrated response is a vine propagation standard, which supplies the sector with healthy grapevines. A standard for the propagation and supply of grapevines is being developed in a separate project and, once adopted across the supply chain, will provide access to certified virus-free grapevine planting material. Continual interchange between the standard and other parts of the integrated response – virus detection, removing virus-infected vines, and vector awareness – offer growers the best prospect for managing viruses effectively.
As acknowledged in the guide, the Australian situation is likely to be more complex than that in New Zealand. We grow a wide range of grapevine varieties across many climatic conditions and management practices. Furthermore, the range of viruses and insect vectors present is wider than in New Zealand, and potentially poorly understood. However, basic management principles are likely to be similar between countries. Hence, where it is feasible to do so, the document provides definitive guidance. Otherwise, knowledge gaps requiring further study are highlighted, and a separate gap analysis document has been provided to Wine Australia to help prioritise future research. The current document will be regularly reviewed to provide legitimacy, ensure it remains fit-for-purpose and to incorporate improvements to practice standards.
In the meantime, it is important to note that grapevine viruses will continue to spread if those affected by them choose to do nothing. This guide acts a starting point for awareness and a call to action for the Australian grape and wine sector to better manage the viruses affecting production and vineyard longevity.