Based on the results of rigorous studies, consultant and grower Christian Abud says the technology is a matter of "life or death" for Chile's gold kiwifruit industry. 

As one of the country's leading producers of the Jingold variety, the manager of C. Abud & Cia knows what it means to lose orchards to the deadly vine disease Psa.

With aims to diversify what was a mono-cultivar sector focused on green Hayward kiwifruit, his company planted 90 hectares of new varieties with its partners in 2008, mostly focused on the Italian-bred Jingold.

Christian Abud inspects some kiwifruit left on the vines to show participants in a field visit.

But after Psa arrived in Chile in 2010, within two years his fields were affected and Abud lost close to 40 hectares of the crop.

"When our fields were contaminated in 2012 that was a turning point, adding to the frosts which meant the bacteria could develop better in tissues which were weaker or damaged," he told www.freshfruitportal.com during a seminar held by the company in Curicó last week.

"Eventually this led to a very questionable situation, and as the bacteria spread it destroyed gold orchards."

But like his kiwifruit-growing peers in New Zealand, Abud was not about to believe the dream was over and set in motion a series of experiments with support from state innovation entity Corfo to test how plastic covers could change the health of plants and in turn, the fruit.

The results are no less than astounding and during a field visit were described by one of his agronomists as a "glimmer of hope", and a "window of opportunity" by Chilean Kiwifruit Committee president Carlos Cruzat who admitted he was sceptical in the beginning.

On average, the study - in conjunction with Subsole and Agro Desarrollo - showed the yield for Jingold kiwifruit fields with covers was 26.23kg per hectare, compared to 15.88kg per hectare for orchards with no covers.

The experiments have shown a stark contrast in yields between covered and open-air gold kiwifruit orchards.

In the two seasons of testing the fruit was also more uniform in size and shape, the plants needed fewer nutrient inputs to garner the same phosphate and nitrate levels, and the environment was also warmer which is crucial in times of frost.

"If you were to get a frost event like what happened in 2013 or spring rains like in 2015, it pays for itself," said C. Abud & Cia technical manager Raimundo Cuevas.

Cuevas added the warmer temperatures also limited the bacteria's development while the covers kept the leaves dry, limiting the pathogen as it needs water to multiply and move.

Nonetheless, plastic covers can cross the budget threshold for many growers under strain from difficult growing conditions and markets. This is why Abud emphasized growers cannot just pick any material, like what is often used by cherry growers to avoid cracking, but high-end products.

Cuevas said the covers and structures would cost US$18,000-20,000, with new materials costing US$9,000 five every three or four years.

"Over 10 years that's around US$3,800 per hectare each year," he said.

But do the potential revenues justify the costs?

Growers in areas unaffected by the disease have been reluctant to make such large capital outlays, but Abud emphasized that as the disease spread further in Chile the technology would become more attractive, and it was a good idea to adopt covers to boost plant health before the disease hits.

"To be able to subsist with Psa in gold kiwifruit is good business," Abud said.

"Think of it as like having a person who's sick with tuberculosis. If you put them in the garage and allow them to be cold, clearly the patient will die.

"In contrast, if you put them in ICU (Intensive Care Unit) with all the perfect conditions and medications, obviously their defenses will improve. For us, we’ve altered the climate of or orchards and strengthened our plants so they are comfortable to live with the disease."

He said Psa would be impossible to eradicate, but the industry could continue and thrive if the pathogen were to be reduced in individual farms.

"We were resigned to plants living together with Psa and having a similar production to a good orchard, but we realized the covers help produce more fruit and better quality."

Abud's team and researchers from various Chilean universities are now studying how they can make irrigation more efficient with the covers, and are also looking for ways to improve cover structures; in the tests to date, retractable covers have had positive results but fixed covers have not fared so well because bees get confused inside the environment, prompting pollination difficulties.

Additionally, the level of soluble solids - a key factor for fruit sweetness - were marginally lower for the fruit grown under covers, but Abud believed this may not impact final brix levels as the fruit would get sweeter in storage.

Whether this hypothesis is true will be clarified at a seminar to be hosted by the company in August.

"When you cut a grape from the vine and it has 17° brix, that's where it stays, but when you harvest a climacteric fruit [like kiwifruit] you harvest with a certain sugar content and a store of starch...with pre-ripening it can reach its maximum potential."

It is understood that New Zealand kiwifruit marketer Zespri has upped the ante this year on its acceptable brix levels, so we asked Abud whether gold Chilean fruit grown under could keep pace with their trans-Pacific counterparts.

"Our gold kiwifruit can compete one-on-one with Zespri, and also the plastic covers and the temperature regulators make the fruit more uniform," he said.

"One of the big factors at the moment is the heterogeneity of the fruit, but that comes from a structural issue. The Hayward kiwifruit were planted around the year 2000 and since Psa they haven't been renewed so you have a base for some kiwifruit vines which is at 50%.

"The orchards, when they get old, are just like human beings - there are more imperfections."

And as the vine disease spreads, the message is not just about the renewal of vines and varieties, but a rethink of Chile's kiwifruit production methods.

"I remember when I started using drip irrigation and people thought it was too expensive. Now everyone is using it, and I think something similar will happen with plastic covers."

www.freshfruitportal.com