Featured image above: Plant Biosecurity Cooperative Research Centre
Phylloxera is an aphid-like insect that is a pest of commercial grapevines worldwide. The Plant Biosecurity Cooperative Research Centre (PBCRC) is funding a project led by Vinehealth Australia to conduct field trials for a new, accurate, sensitive and cost-effective DNA-based test for detecting the pest.
CEO of Vinehealth Australia, Alan Nankivell, who is leading the project, says phylloxera had a significant economic impact on the wine industry, as “the quality of our wines is based on the quality of our vines”. Eighty per cent of Australia’s vineyards have vines that are own-rooted, rather than grafted onto resistant rootstock; some are very old and the wines produced from these are highly sought after.
Phylloxera (Daktulosphaira vitifoliae) feeds on grapevine roots and leaves them open to bacterial infection, which can result in rot and necrotic death due to cell injury. It destroyed substantial areas of vines in France in the mid-19th century and has affected several winegrowing areas of Australia; the only effective treatment is removing infested vines and replanting with resistant rootstock.
Financially, the cost of managing a vineyard with phylloxera is estimated to range from 10–20% in additional operating costs.
The current method of detection uses a shovel and magnifying glass to inspect sites in areas of low vigour; however, phylloxera may have been present for some time and the test is usually conducted in summer, one of the industry’s busiest seasons.
The new DNA-based test requires 10-cm soil core samples to be taken 5 cm from the vine’s trunk. The samples are then sealed and sent to a lab where they are dried and tested for the presence of phylloxera DNA.
Nankivell says the incidence of finding phylloxera using the test was very high (around 98%), even when the amounts of phylloxera present were low.
“At the moment, we’re able to find phylloxera at sites any time of the year.”
The new DNA-based test could help prevent the spread of phylloxera in Australia, as those who have it on their property can determine where it is and whether it is spreading.
Sampling in vineyards across Australia over time will establish a baseline for the maintenance of area freedom. Nankivell says with this baseline in place, the quarantine management and farm-gate hygiene of vineyards will improve industry knowledge about where phylloxera is and isn’t.
PBCRC researchers are currently working to establish the most suitable grid pattern for taking the soil core samples.
They will also compare the DNA sample method with two other methods: the ‘shovel method’ and another using emergence traps to catch insects inside an inverted container placed on the soil, to determine performance against selected criteria.
This research strongly supports the wine industry’s focus on identifying and managing biosecurity threats to ensure the ongoing health of grapevines. Healthy vines are the foundation for a prosperous Australian wine industry.