Imaging offers benefits for vineyard management

In the brave new world of vineyard management, the once imponderable is happening: spotting irrigation flaws and vineyard viruses without a human being on the ground touching the vines.

It's done remotely by eyes in the sky and all-terrain vehicles on the ground.

The San Joaquin Valley Winegrape Growers hosted a discussion of the technologies with John Bourne, vice president of marketing at Ceres Imaging, and Luca Brillante, assistant professor of viticulture at California State University, Fresno, and Bronco Wine Co. viticulture research chair.

Bourne's talk opened with him pointing out that Ceres won a global Zayed Sustainability Prize in the water category for reducing water use by 10%.

Bourne talked of challenges to farming that include drought, severe weather, wildfires and employee shortages. He said per-acre yields for grape growers may drop by 5% to 15% by 2040, according to a study by the University of California, Davis.

But on the brighter side, he pointed to technical innovations, some decades old, that have brought significant benefits. They include the use of aerial photography that began in 1933 to detect viral diseases in potatoes, satellite imagery that has been used since 1972 for global agriculture and artificial intelligence that in 2013 was put to use for imagery crop modeling.

Bourne said thermal images can be critical for irrigation management, "catching issues two to three weeks before they're visually apparent." Those images show temperature differences as slight as plus or minus .01 degree Celsius.

Some 38% of winegrape growers reported using imagery on an ongoing basis in 2020, Bourne said.

Imagery platforms for irrigation management include use of drones, fixed-wing airplanes and satellites.

"Ceres does not use drones because of the inability to carry the payload," Bourne said. "Thermal cameras are too heavy, and flight times are 30 minutes or less."

He said use of satellites is "cheap," but a downside is that they provide low resolution. Ceres uses primarily fixed-wing aircraft to get high resolution images of a whole orchard or vineyard.

"It's the best platform for thermal imaging," Bourne said.

He said irrigation management with flyovers can result in detection of irrigation issues, improved uniformity management and performance measurement, and improvement in applied water optimization.

Bourne said benefits of using imagery to manage irrigation can include increased yields, increased water-use efficiency, protection of crop health, improved crop quality and "more efficient use of your time and labor."

He quoted Kyle Moeller, senior irrigation systems specialist with Fowler Packing in Fresno County, saying, "If you walk a field, you maybe walk one or two rows and say, 'Sure, I've got a little problem here,' but you don't always grasp the full extent of it."

Patrick Tokar, a viticulturist at Rombauer Vineyards in Napa Valley, said, "What we did not realize when we first started using the service is the amount of correlation between water stress areas and wine quality."

Bourne said a good resource for learning what Ceres offers is at support.ceresimaging.net online.

Brillante said he and other researchers acquire imagery of leaf samples in a laboratory dark room, from the side of the canopy with a tripod and with an ATV, as well as with drone and high-resolution satellites.

"Satellites are the easiest to scale, but not the most accurate," Brillante said. "Drones are less scalable but most accurate, have a higher resolution, and we have direct control over the sensor."

Researchers use two hyperspectral cameras, and Brillante said hyperspectral satellites are not yet available.

Brillante and others concentrate on red blotch and leafroll, and are able to sense the presence of a virus before the symptoms are visible.

A sensor system records electromagnetic radiation detected as a combination of reflected solar radiation and that which is emitted by an object.

Grapevine red blotch was first reported in 2008. It is often spread through propagation of infected nursery stock, and the vector is the three-cornered alfalfa hopper.

It's believed grapevine red blotch may reduce carbon translocation, leading to impaired berry ripening. It can result in stomatal limitation, or reduced transpiration and photosynthesis. It also impairs sugar translocation from leaf to berry.

Brillante said the cost of virus infections in vineyards with an average lifespan of 25 years ranges from $10,000 to $16,000 per acre. With 880,000 aces in California, the annual cost to growers could reach hundreds of millions of dollars per year.

It's not possible to treat viruses, Brillante said. The only solutions are using plant certified material, which can become infected, and "scouting and rogueing for infected vines," which is costly and only effective at an early stage.

(Dennis Pollock is a reporter in Fresno. He may be contacted at agcompollock@yahoo.com.)