Source: Capital Press

The possibility of using unmanned aerial vehicles for pesticide spraying is more than just hype, according to an agricultural engineering expert.

The excitement over drones has led farmers and entrepreneurs to conjure up many potential uses for the devices, said Ken Giles, a biological and agricultural engineering professor at the University of California-Davis.

“When you have a new hammer, everything looks like a nail,” he said at the recent Precision Farming Expo in Salem.

However, Yamaha’s R-Max helicopter shows promise in spraying pesticides in areas that are challenging for conventional ground and aerial applicators, Giles said.

Wine grapes and other specialty crops are sometimes grown in irregular configurations on slopes and in the vicinity of trees — awkward conditions for existing spray systems but ideal for unmanned aerial vehicles, he said. Tests conducted in 2013 and 2014 show that the UAV can treat 3-7 acres per hour, compared to 1 acre per hour or less with ground-based sprayers, Giles said.

In terms of chemical deposition on the crop surface, the unmanned helicopter performed the same as aerial and ground applications, he said. Chemicals were applied more uniformly with the UAV compared to ground spraying because of the air movement caused by its rotors, Giles said. A drawback of the technology is that the helicopter can only hold up to 4.2 gallons of liquid, he said. The capacity constraints will necessitate working with concentrated levels of chemicals.

“We are sensitive to payload limitations and this will certainly be a factor in any spraying that we do,” Giles said.

The UAV is already used by farmers in Japan on rice fields but the university is conducting studies in the U.S. to assure pesticide and aviation regulators that the device can be used safely here. Using ground-based robots in specialty crop production also presents opportunities but such technology continues to face practical challenges, said Qin Zhang, director of Washington State University’s Center for Precision Agricultural Systems.

Advanced robots are used in manufacturing but agriculture poses unique problems for such machines, he said. Identifying and harvesting fruit, for example, is difficult in a biological system.

“Every tree is different, every apple is growing in a different location and orientation,” Zhang said.

The mechanism for picking, while simple for a human, requires twice as much force for a robot and thereby will cause more bruising, he said. Apart from the technical hurdles, robots need to be affordable and simple to operate for users, Zhang said.

Even so, the declining availability and increasing cost of labor means researchers must tackle these issues before the situation is dire. For example, by the time an automated asparagus harvester was developed, the U.S. asparagus industry was already greatly diminished, Zhang said.

“We cannot wait, we need to react now,” he said.