Disease threatens older vineyards

New Zealand is known for its new world wine, but as vineyards start to age their susceptibility to the crippling trunk disease is increasing.

Winepress, the official magazine of Wine Marlborough, reported in June that Villa Maria winery conducted a survey on its older plantings, to get a handle on the extent of the problem.

Winepress reported that all of the vines tested were infected and 20 per cent of the vineyard was beyond remedy.

Grapevine Trunk Diseases (GTD) is caused by fungal infections and threatens the longevity of vineyards internationally.

Marlborough Plant and Research senior scientist, Dion Mundy has been studying grapevine trunk disease since 2007.

‘‘Research has been done internationally, but we need to modify this for New Zealand and our environment,’’ Mundy said.

Wine Marlborough general manager Marcus Pickens said awareness of the disease had been a bit of a slow burner.

However, Pickens said as vineyards started to age, the industry had started to become more aware.

‘‘There are some concerns out there, there are some mitigation strategies that people need to start implementing, people need to be fairly robust,’’ Pickens said.

The prevention strategies were part of the ongoing work Mundy and his team have been researching.

While the disease affected both Hawkes Bay and Marlborough vineyards, Mundy said Sauvignon Blanc vines were more susceptible.

Mundy said the focus is to intervene early. The first symptom of trunk disease was stunted growth.

The Villa Maria vineyard showed visual signs in 4 to 5 per cent of the trunks, Winepress reported.

‘‘At the moment the best intervention is to cut out the disease and allow the vine to do what vines do very well, which is to grow new wood,’’ Mundy said.

The vine is then trained to form a new trunk and the old trunk is removed – this was effective if the disease was discovered early.

The trunk was then painted with wound dressing.

The vine would then be renewed in the retrunk process and around one year’s yield would be lost, as the process takes around 18 months. ‘‘It comes back into full production after that,’’ Mundy said.

‘‘We’re seeing this in Hawkes Bay and Marlborough because the New Zealand industry is being proactive.’’

Plant and Food Research and New Zealand Winegrowers had also looked into different methods of sprays to put on the wounds instead of painting.

Four sprays had been registered as a result of this research.