Maximising the good oil
Olive growers have more than doubled production using new techniques, which could expand the local share of the olive oil market to 20 per cent.
Wairarapa grower Craig LeafWright, 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.
A three-year trial by Olives NZ and supported by the Ministry for Primary Industries through its
Craig Leaf-Wright
Sustainable Farming Fund, has also improved the problem of biennial bearing, where a crop is heavy one year and light the next.
Kiwis are estimated to spend $35 million per year on 4.5m 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 pulled out 1200 trees because we were chucking every chemical known to man at them and we did not 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 are 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 were not generating any new young wood,’’ LeafWright said.
Olives fruit only on new wood.
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 has set.
Tustin said there were big differences between how olives grow in New Zealand and in their traditional Mediterranean home. New Zealand’s olive trees are adversely affected by a wetter climate, whereas around the Mediterranean insects were a big problem.
‘‘In New Zealand there are three critical wet weather diseases which affect the trees. Olives are evergreens and when they get the diseases they drop leaves . . . it affects cropping enormously. We are using a broad spectrum fungicide which
is used for many crops; it has been in use for 60 years.’’
Olives NZ executive officer Gayle Sheridan said the techniques were tried on five olive groves, one in each major growing region.
After one year, the result was so dramatic that the growers on the trial blocks insisted on extending the methods to their entire groves.
‘‘Once diseases began to be controlled, we found we were able to grow large clusters of olives for the first time – like bunches of grapes.’’
Tustin said the best regions to grow olives in were on the east coast from Bay of Plenty south, including Central Otago, with a maximum rainfall of about
800 millimetres a year.
‘‘But there are some very good groves in Nelson, Bay of Plenty and Ka¯ piti which have closer to 1200mm of rain.’’
One of the biggest problems is that olives are picked late – from May to July – when early frosts can damage the fruit.
Olives NZ has received MPI funding for a further three years to see if production can be further extended. The new project aims to produce an additional 5kg per tree, and will include revising harvesting methods. It will also trial organic methods of production.
The funding of $108,000 will come from a combination of MPI and industry. ‘‘Many small growers don’t have the right equipment to undertake spraying and don’t want to spend the money on it – and other don’t wish to spray so intensively,’’ Sheridan said.
‘‘Part of our research will include experimenting with a programme for disease control using organic principles based on apple orchards.’’
About 300 olive groves cover more than 2000 hectares across New Zealand.
‘‘In the early days . . . we failed to notice the fruit was growing on the outside of the tree, not on the inside.’’