Grape-bug threat nothing new, says viticulturalist

A virus spread by mealy bugs that reduces the yield and quality of grapevines has been in Hawke's Bay for at least 10 years, a viticulturalist from Te Mata Estate Winery has said.

Larry Morgan was responding to a New Zealand Winegrowers' report highlighting the devastating consequences of the leaf-roll type-three virus.

"Most wineries take one of two vines out each year to control the bug, which can spread from vine to vine," Mr Morgan said.

"We have a regular spraying programme to keep on top of the mealy bug.

"We spray them, just as they're coming out of dormancy, with a growth regulator which doesn't kill other beneficial insects such as ladybirds.

"I don't think many winegrowers would let their vineyards get that bad so they'd need to rip out whole blocks," he said.

The report said that a vineyard completely infected with the virus could cost the grower $12,000 a hectare a year, with total replanting costs of $57,000 a hectare.

It urged growers to keep a constant watch on their vines and pull out diseased vines immediately, and cited Hawke's Bay and Gisborne as the worst- hit regions.

CJ Pask vineyard manager Bruce Smith said Hawke's Bay's warmer climate made it more susceptible to mealy bugs than other New Zealand winegrowing areas, such as Otago.

"The virus has been here for many years, but what we're trying to do is find more ways of controlling it.

"We spray vines at the start of the season, which, depending on the varieties, is usually around September or October.

"We have removed about six or seven hectares in the past three years. CJ Pask has the oldest vineyards in the Gimblett Gravels area, and the virus is totally related to the vines' age.

"The main thing we have to get a handle on is how this virus actually works, so there is still a lot of scientific research to be done," Mr Smith said.

- HAWKE'S BAY TODAY