SEEDS OF DISCONTENT
They’re the fruit we love so much we named it after ourselves – but now, writes Chloe Ranford, the humble kiwifruit has grown into a pest that could ruin our native vegetation and major agricultural industries.
FARMED kiwifruit may bring millions of dollars as an export but its wild cousin is being branded a ‘‘hellish’’ pest that’s damaging native bush and threatening the nation’s vineyards.
Kiwifruit Vine Health analyst and compliance officer John Mather said it was highly unusual for an industry to turn in its own produce as a risk.
‘‘It’s not often a member of an industry comes forward in the hopes of naming their produce a pest,’’ Mather said.
Mather took his case to a pest management meeting in Marlborough last week, saying wild kiwifruit could threaten the region’s celebrated wine industry.
‘‘Not only does wild kiwifruit impact indigenous biodiversity and production of forestry, it’s also a reservoir for disease organisms such as PSA and pests such as fruit flies and stink bugs,’’ Mather said.
‘‘If these pests or disease got into Marlborough vineyards, it could have a detrimental effect on their growth.’’
New Zealand Winegrowers biosecurity manager Ed Massey said the brown marmorated stink bug, a known kiwifruit hitchhiker, was a ‘‘high-risk’’ threat to the wine industry.
‘‘Not only do they eat the grapes, but they taint the red wine,’’ Massey said.
‘‘The defensive chemicals the bugs release when crushed affect the red wine juice and its quality.
‘‘Should a population establish thanks to wild kiwifruit, Marlborough vineyards would have a lack of surveillance and control tools available to combat the threat they’d prevent.’’
Motueka’s Golden Bay Fruit owner Kerry Wilkins said vigilance in the orchard was key to preventing wild kiwifruit growth in the South Island.
‘‘Kiwifruit that does fall to the ground gets blended up in the mower to prevent it from spreading elsewhere,’’ Wilkins said.
‘‘Good hygiene in the orchard, like washing your hands, and being vigilant are two crucial aspects to preventing wild kiwifruit spread.
‘‘While it’s a plant that sometimes grows in the area, it’s not a big problem right now.’’
But on the other side of New Zealand, in the Bay of Plenty, wild kiwifruit was a much larger issue.
‘‘In these areas, wild kiwifruit rapidly forms a heavy blanket of growth which kills, or topples, native trees and shrubs beneath,’’ Mather said.
‘‘Since 2010, Kiwifruit Vine Health has killed around 14,600 wild kiwifruit vines in Bay of Plenty and Te Puke.’’
New Zealand Kiwifruit Growers Inc chief executive Nikki Johnson said kiwifruit grew well in New Zealand because it boasted some of the ‘‘best growing conditions in the world’’.
‘‘Clean air, fertile soils, a cool ocean, generous climate, and fewer pests and diseases all contribute to the unique quality and taste of New Zealand-grown SCOTT HAMMOND / STUFF seeds per fruit and these have a high likelihood of germination,’’ he said.
Mather said wild kiwifruit outbreaks were ‘‘exacerbated’’ by unpicked fruit.
‘‘Any fruiting vines that aren’t managed properly are targeted by birds who eat the wild kiwifruit and then spread the seeds into areas of native bush, forestry blocks and near orchards or farms,’’ he said.
Kiwifruit scraps were also said to be a major cause of wild kiwifruit flare-ups.
‘‘We’ve found kiwifruit stickers near wild kiwifruit vines, which proves the vine sprouted as a result of someone throwing their scraps out,’’ Mather said.
‘‘What’s interesting is that because kiwifruit stickers are changed each year, we’re able to find out in which year the scraps were originally dumped.’’
Wilkins said South Island kiwifruit farmers were concerned about a wild kiwifruit outbreak because the fruit often harboured vine-killing disease PSA.
‘‘At the moment, our district is PSA free,’’ Wilkins said. ‘‘We spray farmed kiwifruit for disease control purposes, but wild kiwifruit doesn’t receive this treatment.
‘‘Everyone is concerned about wild kiwifruit because the PSA it could harbour would be quite detrimental to the industry.’’