Yamaha helicopter drones have been used for 25 years in Japan for spraying chemicals over rice and other crops. Recently the company has been testing the aircraft in California’s Napa Valley to spray a preventative fungicide to keep powdery mildew from forming on grapes.
 
It makes you wonder if a helicopter drone would ever be used to spray or drop water or retardant on a wildfire. In 2015 Lockheed Martin and K-Max demonstrated the use of a full size drone, an optionally-piloted K-MAX, to haul external loads and drop water.