The stress level among vintners in New Zealand's Central Otago region has ticked up a notch, following confirmation last week of another infestation of the destructive root louse phylloxera. This is the second such discovery in Central Otago, which until 2002 was thought to be free of phylloxera since the parasite typically prefers ground softer than the region's sandy, rocky soils.
"This is a bit of a wake-up call for everybody," said Martin Anderson, president of the Central Otago Winegrowers Association.
This infestation appears to be confined to a relatively small subsection of Central Otago, which is known primarily for producing Pinot Noir. The pest was found in about 580 square feet of a vineyard in Lowburn, located near the center of Otago. The town is about 25 miles northwest of Alexandra, the site of the region's previous phylloxera infestation.
Options are limited once phylloxera establishes a toehold in a viticultural area. The aphid feeds on vine roots, starving infected plants as they gradually lose their ability to ingest nutrients. The only solution is to uproot infected vineyards and replant them with vines grafted onto rootstock that is resistant to the pest.
The European vine species Vitis vinifera—which includes the world's finest grapes, such as Pinot Noir—is particularly susceptible. Native to the New World, where the local vine species developed resistance, phylloxera first arrived in continental Europe in 1862, on a batch of American vines sent to a grower in the Rhône. (Read a history of phylloxera here.) By 1890 it had devastated vineyards throughout France; the country's wine industry was saved only by grafting vinifera onto the rootstock of a hybridized native American variety. In California, during the 1980s and 1990s, a mutated form of phylloxera forced growers to replant tens of thousands of acres of vines, at a cost of more than $1 billion.
It looks as though replanting will be necessary at many estates in Central Otago, where about 40 percent of the region's 2,800 acres of vines in production are on native rootstock. "We have to accept that over time it will come our way, and someday we'll have to do some replanting," said Jeff Sinnott, winemaker at Amisfield, which has a vineyard located about two miles from the site of the most recent outbreak.
Only 15 percent of Amisfield's vines are on native roots, leaving Sinnott with better prospects than many Otago producers. The region's older estates were planted by the mid-1990s, before many non-native rootstock options were widely available in New Zealand. And expansion in Central Otago has been so explosive—vineyard acreage in the region increased tenfold in the last decade, according to the trade association New Zealand Winegrowers—that even some recent plantings have native roots, though it's predominantly older vineyards that are at risk.
There's no way to pinpoint the source of the current infestation. To date, only one type of phylloxera has been identified in New Zealand's different viticultural regions. The best-case scenario is that the insects in Lowburn arrived from the Alexandra site, rather than from another, as-yet-undiscovered outbreak.
After the discovery of Central Otago's first phylloxera infestation, growers established protocols intended to slow its spread. These include restricting the movement of vehicles between vineyards and cleaning shoes and equipment. "The protocols will certainly be practiced with great regularity from now on," Anderson said, but admitted, "I'm not sure they have been in the past."