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The Raven spray controller has brought major improvements to orchard spraying.

The Raven spray controller has brought major improvements to orchard spraying.

Courtesy Blueline Equipment

A major breakthrough in orchard spray technology in the last decade has been a rate control system that automatically calibrates sprayers during spraying, saving countless gallons of crop protection chemicals. Future spray technologies could include sprayers that are site specific, sense and adjust for canopy density, or are fixed systems that eliminate tractor-pulled spray rigs.

Gwen Hoheisel, Washington State University Extension educator and leader of a spray application research project funded by the Specialty Crop Research Initiative, said that the Raven rate control system was “the biggest breakthrough” in orchard and vineyard spray technology in recent years. The technology, developed for boom sprayers used on field and row crops, allows growers to better control application rates, even if tractor speed changes.

Gregg Marrs of Blueline Manufacturing and Equipment Company, Moxee, Washington, agrees that the Raven rate control system, named after the company that makes it, has had a big impact on spray applications.

“Sprayer calibration involves knowing ground speed, pressure, nozzle size, and diameter,” Marrs said, explaining that the Raven rate system accurately measures speed, uses row spacing, and automatically calibrates the amount of spray that’s been programmed.

Spray rig calibration is necessary to know accurately how much pesticide is being applied, but sprayers are often improperly calibrated, resulting in more pesticide being applied than intended.

“Ground speed is different than tractor speed, and it changes when you’re going uphill or downhill,” he said. It’s really difficult for a tractor driver to maintain an exact, constant speed in an orchard, but speed greatly affects rate. It’s also difficult to accurately measure nozzle size, as wear and tear of nozzles can change the spray pattern.

Since the Raven rate system was adapted for orchard sprayers ten years ago, Marrs has sold about 1,000 units.

“If you can improve calibration by 15 percent—which is a low number—you can save 15 percent in material that’s applied over the course of the year, not counting operator time,” he said. “Considering that an average orchardist applies $30,000 to $40,000 worth of chemicals in a year, that 15 percent savings (from $4,500 to $6,000) is significant.”

The Raven rate system can generate a two-to-one return on investment, he added.

While tower sprayers have greatly improved the delivery of sprays through better targeting, he still believes that the rate control system has made its mark on the tree fruit industry.

“Of all the spray application technologies in the last decade, the greatest one-time effect of any technology has been the Raven rate control system,” Marrs said. “And it’s not just a cost factor—there are worker safety and environmental benefits from improving the rate and delivery.”

Future technologies

WSU’s Hoheisel, who leads a team of researchers charged with developing a smart targeted spray application technology roadmap for specialty crops, said that several emerging technologies could be “game changers” when it comes to tree fruit and grape pest management.

“The Raven rate control system has been a big step forward, but we need to continue to keep improving application techniques,” she said, identifying canopy density sensors as a future spray technology holding great promise.

A game changer for pesticide applications would be a fixed or solid-set delivery system that sprays chemicals over the top of tree or vine canopies similar to an overhead evaporative cooling system. Hoheisel notes that an SCRI funded research project is underway to study such a system.

“Growers never have enough sprayers when timing is crucial,” she said, adding that a fixed system would have a huge impact on worker safety by getting the ­applicator off the tractor.

In looking at the crystal ball of spray technology, Marrs predicts that the next round of sprayer improvements will be development of site-specific technology similar to variable rate technology used to apply fertilizer. He envisions technology that will allow the use of multiple products injected into the spray fluid as needed.

An orchard would be mapped first with Global Positioning Satellite coordinates to identify pest and disease hot spots. Information would be downloaded into the spray controller, and the sprayer, carrying multiple crop protection chemicals, would apply specific pesticides only   where needed.