Vineyards on alert for frost damage

Frosts this week are endangering new buds and leaves on Wairarapa's vineyards, and the Met Service says there is more to come.

Vineyards have had frost fighting machines in action over the past two mornings, and the Met Service has warned they may be needed again next week, and ahead until mid-October.

Met Service spokesman Bob McDavitt says anticyclones over the next month will bring clear skies and more risk of frost.

The next month should also be standard for rainfall, but by mid-spring and summer the weather could become dry.

Peter Caldwell, winemaker at Te Kairanga wines in Martinborough, says pinot noir and chardonnay grapes are vulnerable at the moment, with sauvignon blanc, reisling and cabernet still to bud.

Vines at the "woolly bud" stage are not quite as vulnerable as those that are showing some leaf, and the more fresh growth showing, the more sensitive the vines are to frost conditions.

Mr Caldwell said there are four main methods of fighting frost – wind machines, sprinklers, helicopters and hot air burners.

The wind machines and helicopters push warm air down to ground level, the sprinklers use the "latent warmth" of water to prevent freezing and the hot air burners heat up the air from ground level.

The method used depends on the size of the area and the severity of the frost, and they are often used in combination.

The worst frost Mr Caldwell can remember was in the spring of 2002. That frost saw a "large amount of polar air" which meant the warm inversion layer was higher than the wind machines and helicopters could easily reach, and they were just moving more freezing air around.

"I don't think there was anyone that was unaffected," Mr Caldwell said

- WAIRARAPA TIMES-AGE