Of the pests and diseases already in Australia, our greatest biosecurity threat to grapevines is grape phylloxera. We have some of the oldest vines in the world and with estimates that at least 70% of Australia’s winegrape vineyards are planted on own roots, and thus susceptible to phylloxera attack, continued work on improving phylloxera detection methods is vital.
Active surveillance for grape phylloxera is what we must prioritise, and that requires practical and effective tools for growers and regulators alike.
Traditionally, surveillance for phylloxera is undertaken by a third party, often regulators and not growers themselves. The current endorsed phylloxera detection method called ‘visual root inspection’, requires a small portion of roots to be dug up and inspected by trained personnel using a x10 magnifying glass. This method is time consuming, expensive, and relies heavily on the capabilities of the inspector.
Therefore, a simple, rapid, sensitive and accurate method for the detection of phylloxera is needed to enhance grower uptake and to simplify surveillance activities for regulators. This will improve the chance of detecting where phylloxera is and is not, and thus enable protection of vineyards from phylloxera.
Additionally, the development of a test that enables rapid collection and analysis of samples will greatly assist not only general surveillance activities, but also management in the event of an incursion.
Vinehealth Australia was the lead agency in a recently-completed collaborative phylloxera research project, to develop an additional phylloxera detection system using DNA extracted from soil samples. Outcomes of this project are expected to support identification and verification of area freedom status to facilitate market access for growers, as well as improving proactive management strategies for phylloxera.
The five-year project was funded by Wine Australia and the Plant Biosecurity Cooperative Research Centre (PBCRC). Partners in the project included South Australian Research and Development Institute (SARDI), Rho Environmetrics, the University of Adelaide, the Victorian Department of Economic Development, Jobs, Transport and Resources, Biosecurity SA (PIRSA) and the NSW Department of Primary Industries.
This research project has successfully developed a field sampling protocol for collecting soil cores and validated a diagnostic protocol using qPCR (quantitative polymerase chain reaction) for the detection and quantification of phylloxera (‘DNA method’). The estimated detection limit was determined to be 2 phylloxera per 200g dry soil composite sample.
The field sampling protocol developed, involves the use of a simple soil corer to collect soil samples within 10cm of a vine trunk and to a depth of 10cm. Some bulking of soil cores into a single sample can be undertaken to reduce laboratory costs, however this has the potential to reduce phylloxera detection capability in blocks where infestations are isolated or quantity of phylloxera present is low. Samples can be collected at the current density outlined in the National Phylloxera Management Protocol (NPMP) of one vine in every 3rd row, every 5th panel. However, higher sampling density may be warranted for any blocks suspected to have a low or isolated phylloxera infestation. In addition, continued evaluation of weak vines as part of any phylloxera surveillance strategy is recommended. Samples must be stored at no more than 20°C during transport and reach the laboratory within 48 hours of collection.
Detection rate of phylloxera was evaluated over different times of the year across multiple years. Higher amounts of phylloxera DNA were found from late summer to early winter, peaking in autumn, but detection was possible all year round using qPCR. A comparison of the newly developed DNA method to the other primary phylloxera detection methods of visual root inspection and emergence traps, showed differences in detection rates at landscape, block, composite and vine level. Reasons for these differences and the relative strengths and weaknesses of each method were reported.
Endorsement of the DNA method alongside the visual root inspection and emergence trap phylloxera detection methods, will provide growers and regulators with an integrated toolkit of field sampling and detection options to utilise as part of national surveillance plans. This will enable greater confidence in area freedom status, delimiting of incursions and upgrading phylloxera management zone status.
This project delivered significant advancement in the ability of industry and regulators to detect phylloxera, and therefore manage the impact of this devastating insect on vines.
Full commercial deployment of the DNA method and integration into national and state phylloxera protocols and regulations will be achieved after completion of the following which are underway:
- National endorsement of the DNA method as a primary phylloxera detection method by the Plant Health Committee.
- Embedding of the DNA method into the National Diagnostic Protocol for phylloxera.
For further information on the findings of the research project, refer to the following:
- A final report (http://vinehealth.com.au/wp-content/uploads/2018/04/PBCRC2061-FINAL-REPORT.pdf) and appendices (http://vinehealth.com.au/wp-content/uploads/2018/04/APPENDICES-FOR-PBCRC2061-FINAL-REPORT.pdf) submitted to the PBCRC,titled ‘Sampling strategies for sensitive, accurate cost effective detection of grape phylloxera for quantifying area freedom status’ completed mid-2018.
- A final report (https://www.wineaustralia.com/getmedia/5041e2c2-2b23-4574-9e67-5aa71e9de718/PGI1201-Phylloxera-Final-report-AGWA) to Wine Australia, titled ‘Sampling strategies for sensitive, accurate and cost effective detections for quantifying area freedom status’, completed mid-2017.
- Giblot-Ducray, D., Correll, R., Collins, C., Nankivell, A., Downs, A., Pearce, I., McKay, A.C. and Ophel-Keller, K.M. (2016). Detection of grape phylloxera (Daktulosphaira vitifoliae Fitch) by real-time quantitative PCR: development of a soil sampling protocol. Australian Journal of Grape and Wine Research 22 469-477.