Update May 6, 2015: The FAA approved the RMAX drone helicopter for crop spraying on May 1. UC Davis professor Ken Giles told the Associated Press that the drone is best suited for working in rolling vineyards and places that are hard to reach from the ground or with larger, piloted planes. http://ow.ly/MBzp7 

Under the watchful eye of news media and area winegrape growers, a remote-controlled helicopter, fitted with a spray applicator system, was field tested today over a vineyard in the heart of the famed Napa Valley by engineers at the University of California, Davis, and Yamaha Motor Corporation, USA.