Rapid spread of virus-like symptoms in grapevines

A mystery reddening of vines in South Australia has researchers at the University of Adelaide searching for answers.

The virus-like symptoms have been found on vines in regions to the north and south of Adelaide, with growers asked to join the hunt for clues to the cause.

In the red grapevine varieties, reddening of leaves in autumn can be caused either by physiological factors, mechanical damage through harvesters or by viruses.

Reddening is a typical symptom of infection with viruses, especially those limited to the phloem tissue, such as the leafroll viruses.

No grapevine viruses found in Australia are known to be spread via mechanical tools. The main route of spread in vineyards is either by top-working with infected propagating material or by sap-sucking  insects such as  mealybugs and  scale insects.  So far, only the grapevine leafroll-associated virus 3 has been reported to spread naturally in Australia.

In 2011, virus-like reddening of vines has been observed in an apparently random distribution, in both the north and south vine growing regions around Adelaide and samples sent to our lab for diagnosis.

So what could this reddening be due to? Virologist Nuredin Habili and Waite Diagnostics director John Randles make some interesting suggestions in the July edition of the Grapegrower & Winemaker magazine.