NZ avocado exports in line for rot prediction revamp

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NZ avocado exports in line for rot prediction revamp

With a wet climate on the edge of where avocado production is viable and far away from key markets, New Zealand faces a tough task when it comes to shipping the fruit ready-to-eat and avoiding rot problems. For this reason the majority of exports - around 80% - are shipped across the Tasman Sea to Australia, while the rest mostly go to the U.S. and Japan. At we speak with Plant & Food Research (P&F) bioprotection business manager Declan Graham, who highlights ambitious goals to send avocados longer distances to Europe and the scientific grounding that could make this not only possible but consistent.

Photo: Plant & Food Research

Graham says New Zealand's avocado industry is restricted by the types of disease control it can use, as when fruit is harvested in September it has often been on trees for around 12 months.

By the time the peak harvest comes in November the fruit will have been there even longer, and this factor combined with the country's strict residue standards means growers mostly use copper sprays to prevent disease.

"We have a temperate maritime climate and we get a lot of wet weather, so the issue we have is that certain parts of New Zealand can get very wet and there’s a problem there with rots like Colletotrichum and Botryosphaeria," Graham says.

"And even though we’d like to be treating very young fruit with fungicides like Pristine which would be a great way to control rots later in the life of the fruit, it would mean that we’d end up with residues on the fruit that’s ready to harvest.

"Unfortunately for New Zealand that’s out of the question so we’ve had to work out other ways of doing this."

A more precise rot control

These 'other ways' are varied and innovative, one of them being controlled atmopshere.

"Working with very low oxygen and low carbon dioxide atmospheres that we’ve developed and researched here, we’ve been able to find we can actually get the fruit to ripen quickly when it is taken out of the controlled atmosphere, so it doesn’t have the same propensity to go rotten.

"The issue with normal controlled atmosphere is that the shelf ripening process is extended by as much as a week, and a week is long enough for latent infections to come through and show up - we're looking for more of a ready-to-eat product."

The research institute hopes that growers will be able to combine this technology with a rot prediction system in the coming years, but it still in development.

"Another one of our research areas we've undertaken is rot prediction - one of our scientists here has been able to show the link between disease on leaves over the wintertime, and the amount of disease you get on fruit.

"Even though you're spraying copper and you think you’re doing a good job, if you can show there’s been some fungal bodies actually in the leaves, there’s a chance you might end up having quite a high rate of disease in your orchards."

P&F's rot prediction program involves harvesting leaves, crushing them up and conducting DNA tests tha can link disease to particular avocado blocks.

Graham says the method is still in its early days but commercial laboratory testing with polymerese chain reaction (PCR) techniques is expected this year for comparison with the September harvest, then next year researchers will test earlier in advance.

"Validation work that needs to be done is about understanding when you harvest the leaves and at what stage in the year is harvesting the leaves going to give you the best prediction."

Relevance to exports

He says a large scale commercial implementation of this technology would allow exporters choose which blocks are most likely going to provide the fruit that can go to distant markets.

"We're such a long way from our markets, and the New Zealand avocado industry has traditionally relied on the Australian market, but the window for selling there is only a few months, from September through to about December.

"Australia is increasing its own production and sometimes we have a very heavy crop into the Australian market and the marketing window is reduced.

"What the industry here is looking to do is focus on distant markets. We do send to Japan and up to the United States, but one of the issues is ensuring we supply good and consistent quality fruit into those markets."

He adds the diagnosis has the potential to boost returns for growers as well.

"With this, when exporters find a clean block they’ll know that’s ideal, and there’s an opportunity for potentially paying growers a premium for producing top quality fruit out of those blocks – theoretically that could happen.

"If you can show there’s some latent infection inside the leaves associated with these disorders, then there is an opportunity for the growers to be a little bit more thorough or observe those blocks in particular too."

An export destination shift

He says the opportunity for exporting further afield is clear, especially given some Australian companies are re-exporting New Zealand avocados into Asia.

"At them moment about 80% of our fruit goes to Australia, but we’re looking to shift it around a bit – it’d be better if that was a lower figure and that we had stronger markets elsewhere.

"The remainder probably all goes to Japan and the U.S. and there's not much going anywhere else - there are individual exporters now starting to focus on other Asian markets and establish customer bases there, but it's a process."

He says New Zealand does not have access to China but does have access to South East Asian avocado markets. However, the crop is not particularly popular in these countries.

To broaden its horizons, last year New Zealand's avocado industry sent test shipments to France successfully.

"One of our scientists traveled up there to do the outturn work on it, and he was able to get fruit from a couple of different orchards, and was able to see and understand the difference in the outturn based on the quality that went into the container.

"From the day it was picked to the day it arrived in France it was something like 50 days, and yet we still had a line of fruit out of that container that was very good from one particular property.

"There were delays but in reality there are always delays when you do this, so it wasn’t a bad result."

Graham believes consistent avocado shipments to European markets could be underway in two years' time.

Plant & Food Research recently launched a new website 'Growing Futures' with case studies about its successful developments. Click here for more.

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