Olive growers have more than doubled production after trials using new techniques, which could see the local share of the olive oil market grow to 20 percent.
Wairarapa grower Craig Leaf-Wright, who has a 4000-tree grove, said each of his trees was now averaging 25 kilograms of olives a year, compared with the New Zealand average of less than 10kg.
The three-year trials at a cost of NZ$195,000, carried out by Olives New Zealand and supported by the Ministry of Primary Industries through its Sustainable Farming Fund, have also improved the problem of biennial bearing, where a crop is heavy one year and light the next.
Kiwis are estimated to spend NZ$35 million a year on 4.5 million litres of oil, more than 90 per cent of it imported.
Leaf-Wright said the project offered two main solutions to low production: better pruning and disease control.
"We planted 20 years ago and initially we planted the barnea variety but after five years they kept on getting disease we couldn't get rid of. We pulled out 1 200 trees because we were chucking every chemical known to man at them and we didn't like doing that.
"In the early days we fell into the trap of watching the trees getting bigger and bigger and we thought fantastic, we're getting more and more fruit off them, but we failed to notice the fruit was growing on the outside of the tree, not on the inside. We weren't generating any new young wood," Leaf-Wright said.
Olives fruit only on the wood produced that year, not on wood produced in previous years.
Plant & Food Research fruit tree physiologist Dr Stuart Tustin and consultant Andrew Taylor, applied methods that work for stone fruit crops to the olive trees.
This included more aggressive pruning, a proactive spraying programme every 21 days and mitigating the issue of biennial bearing by thinning crops after the fruit had set. More