A perennial problem for New Zealand olive growers is the annual frosts that occur during the ripening season, especially in the south of the country.

Frosts, while not occurring often, have the potential to damage olives trees; delay olive ripening and cause potential losses to the industry, for example, in oil production and table olives.

Researchers from the Agriculture and Life Sciences Division at Lincoln University have been successfully using a new treatment aimed at protecting olives trees from frost damage.

Alex Houliston, Leo Vanhanen and Associate Professor, Geoffrey Savage, who carried out the trial and the subsequent analysis of the olives and olive oil, used a naturally occurring product (glycine betaine) found in many organisms, including plants, to spray the trees.

This is done during the cooler temperatures from mid-summer to just prior to harvest in some olive growing areas of New Zealand.

They didn’t have to look far for an olive grove in which to conduct the experiment, as Mr Houliston, owned a suitable olive grove in Canterbury and was keen to allow it to be used for research purposes.

“We were delighted to find that this product significantly reduced frost damage to my trees,” said Mr Houliston.

“This was the first time glycine betaine has been scientifically trialled on olives in New Zealand although it has previously been used successfully on other crops worldwide.”

The experiment was designed to include trees that were sprayed and others that were not (a control group). The olive trees were sprayed six times while the olives were ripening.

After all the olives were hand picked and measured, the frost damaged and non damaged olives were separated.It was found that both cultivars used (Barnea and Manzillo) were protected by the spray, Barnea more so than Manzillo.

“Glycine betaine already has a role in body metabolism so the increased levels found in the olives could actually be a positive feature,” said Vanhanen.

The oil from one kilogram of olives, using the same ripeness and frosted (or not) proportions, and the control oil were analysed for their fatty acid content. Whole leaves and olives from each sample and control tree were also analysed for their glycine betaine content.

The current era of olive growing in New Zealand began with plantings of five cultivars by Dr Gideon Blumenfeld in 1986.

Mr Houliston carried out this research while a Science and Technology Teaching Fellow at Lincoln University.

The project was funded by Olives New Zealand (Canterbury Branch) with other funding and supply of glycine betaine by TCL Marketing Ltd, Christchurch, and Feedworks, Australia.

A fuller description of the research is found in Olivae No. 108, 2007, published by the International Olive Council.