The potential for unmanned aerial vehicles, often called drones, to up the game of North Coast agriculture has become reality, as Napa Valley now has the nation’s first UAV crop-spraying base.

Yamaha Motor Corp. USA in April opened an office at Napa County Airport for spraying of agricultural land in Napa and Sonoma counties with its RMAX remotely piloted helicopter ( On May 18, a Napa Valley vineyard was the site for the first U.S. commercial crop spraying by UAV.

Yamaha’s UAV team applied a fungicide for Napa-based Silverado Farming Company to stave off powdery mildew — a bane of grapegrowers.

Yamaha has been using RMAX choppers internationally for 19 years, but the quest to use them in the U.S. has been a several-year effort, the company said. The company has been working with the Federal Aviation Administration to receive appropriate certifications and testing the system in the field with the University of California, Davis. A representative from the California Department of Pesticide Regulation witnessed the RMAX flight.

“We’ve been diligently working toward this U.S. milestone for RMAX since 2012, when our research partnership with U.C. Davis began,” said Brad Anderson, a market development manager for Yamaha’s Unmanned Systems Division. “It’s gratifying to have earned support from both the aviation and agricultural communities. RMAX provides a unique and effective solution for spray applications, particularly for grape growers with vineyards on slopes or difficult terrain.”

RMAX is the only licensed unmanned aerial system, or UAS, in Napa.

Brittany Pederson, a professional pest-control adviser and viticulturist for Silverado, watched the May 18 spraying. “The results of those trials and conclusions drawn from work at the Oakville Experimental Vineyards were pretty strong and gave us the confidence to begin our own experiments with the RMAX on privately owned commercial vineyards.”

Benefits cited for UAS spraying include safer and more reliable application of treatments with no soil compaction. Applications via RMAX are said to have proven faster and more efficient than current ground spray applications from four-wheelers, tractors or workers on foot. It provides growers with more flexibility and accessibility to their fields, giving them another option for applications.

In December 2015 Yamaha received Part 137 Agricultural Aircraft Operations Certification from the FAA, said to be the first for an unmanned aerial system. That allowed Yamaha to begin agricultural spraying in the U.S., subject to approval by state and local authorities.

The RMAX system has been in service internationally since 1997 and has logged more than 2 million flight hours treating agricultural acres. Today there are 2,500 Yamaha RMAX helicopters flying worldwide, spraying more than 2.4 million agricultural acres annually. Crops treated include rice, wheat, soybeans and vegetables.