Turning up the Heat

Product enables thermal treatments for pest control, fruit set

By Stephen Kloosterman, Assistant Editor
Published in Fruit Growers News, November 2017

A Napa Valley startup company is bringing winegrapes growers a farming technique of heat treatments that was first invented in Chile. Agrothermal Systems is selling shaft-driven heat treatment devices pulled by a tractor. The Agrotherm XT uses propane-burning hydraulic fan heaters to warm vines with hot air up to 350° F.

The heat can be used to increase fruit set, kill small insects, alternate with fungicide for killing powdery mildew spores – and even, CEO Marty Fischer said, embolden the taste of the finished product.

“It is quite different in the glass from control,” he said.

How it works

Taste: Agrothermal Systems CEO Marty Fischer said the application of hot air activates the plant’s self-defense system, increasing its production of phenol and antioxidants – the main flavonoids in wine. The result is a more complex-tasting wine.

Fruit set: Generally speaking, winegrapes set best in warm, dry conditions.

Pest control: Small pests like mites and thrips are easily killed by heat treatments, Fischer said.

Fungicide: Heat treatments control the development of powdery mildew for a period of six days between applications. Fischer recommends trying it in rotation with a regular fungicide treatment.

The inventor of the technology is Chilean grower Florencio Lazo. A big frost that hit Chile’s O’Higgins region south of the city of Santiago in 1991 killed the better part of his table grapes and plums, prompting him to look for ways of avoiding frost. Eventually, he discovered that heat treatments had other uses, especially when coupled with different venting systems.

Lazo and Fischer met in 2006.

“We ended up buying him out in 2012,” Fischer said. There were possible applications for other crops but “we made our decision to focus our energy on the wine industry.”

Agrothermal Systems put three years of research into the machines before starting sales in 2015. The Agrotherm XT sells for $52,500 and the company has sold about 50 units worldwide.

“The sales slope is slow, because it’s an annual crop,” Fischer said.

The technique’s ability to improve fruit set and yield, however, has been demonstrated in trials on dozens of different vineyard trial and control blocks, Fischer said. Thermaculture showed an average fruit set increase of 23 percent, in trials from 2012 to 2016. Clients have also seen increases in their total yield.

Al Wagner, vice president of vineyards at Foley Family Farms in Napa, said the increases in yield are the main reason he bought three units this season after trials last year.

Wagner’s first reaction to Fischer’s sales pitch was skepticism. “My comment was, ‘I have many, many boat anchors in the boneyard,’” said Wagner, who manages 38 properties, about 4,000 acres total, for Foley.

But trials began, when heat was applied to the tree canopies at critical periods during the onset of bloom, and at harvest the treated blocks showed a profit that came with increased yields.

Another believer in Thermaculture is Mark Chandler, a wine industry veteran who served as executive director of the Lodi Winegrape Commission from 1991 to 2011, and who is involved in Thermaculture treatments and trials.

“We are getting strong results from our treatments in Lodi vineyards this year,” Chandler said. “Bunch weights are up 4 percent to 27 percent on treated versus control sites, depending on variety. Similarly, berries per bunch are up 14 percent to 22 percent, so we are excited to see how the harvest numbers come in. Only a few weeks now and we’ll have the final numbers.”

Art William Tukker, owner of Tinwood Estates and his viticulturist, Adam Slate have been working closely to adapt Agrothermal Systems protocols to the unique challenges of growing grapes in the cool wet climate of England.

“We decided to get an Agrothermal machine this spring because we wanted to increase our fruit set and ultimately final yields which can be a massive problem in our industry. Agrothermal technology has shown very good yield results for grapevines in other less challenging climates,” Tukker said. “We started treatments shortly after bud break. Just last week and before veraison we measured bunch weights and berries per bunch and rachis weight and were greatly encouraged to see 41-51 percent more berries per bunch and 32 percent greater average bunch weight in our Pinot Noir test rows versus control.”

Wagner said his staff found “a noticeable difference” in the taste of wine that resulted from the crops produced from the trials. And while there were some mixed opinions in the wine-tasting room, Wagner said not all winegrape varieties give better quality with lower yields.
Foley Family Farms also ran the Thermaculture device about seven times last season with the goal of the killing pests, and said it was successful in reducing the amount of pesticide that needed to be used.

“Overall, it was a win-win for everybody,” he said. “It was a lower impact of pesticide use.”

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